This PDF file contains the front matter associated with SPIE Proceedings Volume 12935, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

Compensation of phase errors has emerged as a paramount task in fringe projection profilometry. In this paper, an erosion-clustering connected domain segmentation algorithm is proposed to compensate for the phase errors of traditional temporal phase unwrapping (TPU). At the onset, two connected domain maps from the wrapped phase are generated with a threshold value of zero. Then the connected domain adhering parts due to noise and height abruptness are forcibly disconnected by an erosion algorithm. Finally, the separated valid points are clustered based on the minimum Eulerian distance method. The combination of several techniques enables the reconstruction of high-quality 3D geometry and endows our method with the flexibility to redress errors arising from the traditional TPU method. Experimental results demonstrate the effectiveness and versatility of the proposed method, building upon the existing TPU methods that obtain fringe orders.

In order to discriminate the sense of velocity, this paper proposes a laser Doppler velocimetry system based on the phase shift method. First, the expression for the light intensity of the interference field is derived, and the relationship between the interference fringes in time is obtained. Then two signal reception channels are generated by means of optical methods with a phase difference of π/2 between them. Finally, the direction of velocity is identified according to the change in phase between the two signals caused by the change in the direction of movement of the object. The experimental results show that the direction of velocity can be effectively determined by using the phase discrimination method.

There is a growing interest in the development of imaging flow cytometry techniques that can simultaneously capture dual-modality images of single cells on a single detector. In this study, we developed a label-free light-sheet dualmodality imaging flow cytometer that is capable of simultaneously capturing bright-field and two-dimensional (2D) light scattering images of individual particles on a single detector. The system uses the principle of hydrodynamic focusing to make the microspheres flow in a single file. The laser and metal halide lamp beams are combined as light sources, which are directed onto the microspheres, providing 2D light scattering patterns and bright-field images of single particles. The two optical channels to collect the scattering patterns and bright-field images are collected by a single CMOS detector. By employing this dual-modality imaging flow cytometry, we demonstrated the obtaining and analysis of the label-free bright-field and light-scattering images of individual micrometer-sized particles. The label-free light-sheet dual-modality imaging flow cytometry is promising for applications in single-cell clinical analysis.

The aberration characteristics change with the relative position changes of zoom groups has been a key problem for continuous zoom lens design, especially those with large target surfaces. To diminish the aberration, in this study, we took a Positive-Negative-Positive-Positive (PNPP) Mechanical structure for optical compensation, and developed a continuous zoom MWIR lens system with 20x magnification. The system used a cooled detector with a large target surface of 1280×1024 pixel and a 12μm pixel size, which improved observing capability under a 66.5° field of view. We tested the transfer function of the system at Nyquist frequency, which is close to the diffraction limit in a 15~300mm zoom range and the full field of view. We further evaluated our system by ray tracing analysis, pressure angle analysis of the cam curve, and de-focusing amount analysis under a temperature range of -45℃ to +70℃. Results show that our system has a good suppression capability for cold reflection, high image quality under extreme thermal conditions, and a smooth zoom curve.

As the electromagnetic environment becomes more and more complex and strong electromagnetic interference becomes normal, in order to improve the ability of ultra-wideband(UWB) communication under strong resistance and complex electromagnetic environment, the wideband communication anti-interference technology has been applied more and more widely in electronic information systems. Based on the advantages of microwave photonic technology such as ultra-wideband and anti-interference, this paper constructed an ultra-wideband adaptive anti-interference communication system by combining microwave photonic spectrum sensing and high-speed frequency hopping signal generation. In the ultra-wideband adaptive anti-jamming communication system, the spectrum sensing module carries out high-speed real-time sensing of electromagnetic environment, the intelligent processor decides the safe spectrum information according to the spectrum sensing information, and the frequency-hopping signal generation module generates high-speed frequency-hopping signals according to the decision information, which can realize the adaptive anti-jamming of ultra-wideband communication. In the simulation, the 2~18GHz frequency spectrum is perceived at a high speed by using a coherent optical comb, and a frequency hopping pattern is determined according to the perceived information. The frequency hopping signal generation module generates a frequency hopping signal of 20000 hops /s according to the frequency hopping pattern, which improves the adaptive recognition ability of the communication system in the UWB range.

We investigate the photon statistics of two-mode photon-subtracted squeezed vacuum states (TMPSSV), which are important factors to affect the sensitivity and resolution of optical interferometers. The comparison between the photon statistics of TMPSSV and two-mode squeezed vacuum states (TMSV) shows that the non-Gaussian operation has the effect of narrowing the characteristic widths of photon number probability distributions. Different from the super-Poissonian statistical distribution of TMSV, when the initial squeezing parameter is lower, TMPSSV shows a sub-Poissonian statistical distribution which is desirable for enhancing the sensitivity and resolution of interferometers. Therefore, non-Gaussian entanglement based on TMPSSV provides a promising quantum resource for an ultra-sensitivity and super-resolution optical interferometer far beyond the standard quantum limit.

Si₃N₄ microring (MR) stands out as a promising platform in the integrated photonics for optical filter, optical delay lines, generation of Kerr frequency comb and optical computing. In this work, we study the optical temporal differentiation in a designed Si₃N₄ MR array. In order to avoid the limitations of a single MR, which can not reproduce the third peak at the trailing edge when differentiation order is between 1 and 2, a MR array consisting of two add-drop MRs and one all-pass MR is designed. Simulation results show that by reusing the drop port of add-drop MRs, differential orders between 0 to 2 can be obtained from different output ports. Furthermore, we propose an optimization algorithm to select the parameters of MRs. As a result, the differentiation deviations for 4-ps input Gaussian pulse can be minimized when the interior-point method is employed. Calculation results show that the differentiation deviations for orders between 1 and 2 are reduced to around 10%, and for orders between 0 to 1 are reduced to within 33%.

When observing astronomical targets from ground-based telescopes, sequential short-exposure astronomical image acquisition is usually performed, where the astronomical images exhibit constant distortion and quality changes, and atmospheric turbulence makes the captured astronomical images seriously affected by noise and severely reduces the resolution. In this paper, we use a deep neural network-based image distortion registration technique to eliminate atmospheric blurring by registering the sequential short-exposure astronomical images and superimposing the registered images to improve image quality. This paper introduces an attention technique based on the Cyclemorph network, which identifies three attention units on the feature extraction network and uses a self-gating soft attention technique to generate a trainable gating signal that allows the network to associate useful local information and then combines the feature vectors obtained from it to make the final prediction. Additionally, this soft attention method can help with accurate target localisation and boost the network's overall performance. To show how well the method works, it is applied to a collection of image datasets of really photographed astronomical targets as well as a set of image datasets of simulated astronomical targets built by a telescope atmospheric imaging model. The built networks go through independent training and testing. According to the experimental findings, the proposed method can successfully register consecutive astronomical photographs, neutralize the impact of atmospheric turbulence, and raise the resolution of astronomical images.

Tongue diagnosis is a way of aiding the diagnosis and identification of pathological conditions by observing tongue images in Chinese medicine diagnosis. The application of photo chromatography to diagnosis allows for the accurate and comprehensive extraction of tongue features. The main characteristic parameter of tongue diagnosis is color information, so this paper proposes a diagnostic method based on the proportion of the primary color of the tongue and the H-component to assist in the analysis. The method treats the tongue color and moss color as a whole, extracts the pixels and proportions of each tongue color and selects the primary color, uses a threshold method to distinguish between healthy and diseased tongue images based on the primary color proportion, and then uses a gray-scale histogram and H-component histogram to extract each feature parameter to achieve sub-classification of the diseased images. The experimental results show that the method is feasible, more stable and accurate than traditional methods, and can improve the diagnostic efficiency.

The selection of atmospheric sample profiles is one of the key factors affecting the accuracy of the fast simulation of satellite channels, but the mechanism of the influence has not been conclusively established. In this paper, the mechanism of atmospheric sample profile selection and its contribution in the forward modeling are discussed through the analysis of the role of transmittance predictors in RTTOV model. The CO2 absorption channel at 15 μm in the infrared band of FY-3C IRAS (InfraRed Atmospheric Sounder) is used as the study object, and the IRAS laminar channel transmittance factor is established based on the TIGR43 profile database. The comparison tests between the profile temperature anomaly and simulation accuracy in the cold and warm scenarios show that the root mean square error (RMSE) of the simulation for the IRAS temperature detection channel is 0.2 K when all the profiles are involved in the regression calculation, compared with the simulation results of LBL. Within the detection height range of the selected CO2 detection channels, there is a strong linear correlation between the profile temperature anomaly and the simulation accuracy in the warm scenario due to the higher order residual term in the Taylor expansion, and more significant accuracy improvement can be obtained if the profile with larger temperature anomaly is removed from the forward modeling.

Compared with traditional analog infrared focal plane detector, digital infrared focal plane detector has many technical advantages, which is one of the key directions of digital infrared focal plane detector technology. Firstly, this article introduces the development history of infrared focal plane array detectors, analyzes the differences between analog and digital infrared focal plane array detectors. After that, four different kinds of the current direction of infrared focal plane array technology are introduced. Then, this paper analyzes the structure and performance characteristics of related readout circuits, and summarizes the development and advanced research results of various companies in different array size and pixel pitch. Finally, the future development trend of digital readout circuit technology is stated.

High-speed (25 Gb/s) oxide-confined VCSELs operating at 850 nm have gained widespread use in data communications. However, ensuring their reliability remains a significant challenge. This study investigates the reliability and failure modes of 25 Gb/s 850 nm oxide-confined VCSELs through accelerated life testing and failure analysis. The high-stress life tests are conducted under various temperatures and bias currents. Aging data over a finite period are extrapolated using a power function to determine the life corresponding to the failure criterion. The median life is obtained by fitting a log-normal distribution function to the device life under different stress conditions. The precise junction temperature is determined using the spectral drift method, allowing for the extraction of key life parameters: activation energy (Ea) and current acceleration factor (n). The findings demonstrate a significant increase in the activation energy of InGaAs-based 25 Gb/s VCSELs compared to GaAs-based 10 Gb/s VCSELs. Additionally, high-resolution transmission electron microscopy (TEM) is employed to analyze failure samples subjected to three types of stress tests: high-temperature and high-humidity with bias aging, electrostatic discharge (ESD) damage, and high-temperature and high-current aging. Three main failure modes are identified and analyzed: dark line defects, electrostatic breakdown damage, and dark spot defects. These failure modes predominantly arise from the combined effects of the oxide layer's shrinkage stress and the InGaAs quantum well's compression stress within the device. This study provides detailed insights into the reliability and failure modes of 25 Gb/s 850 nm oxide-confined VCSELs, enhancing our understanding of degradation mechanisms in high-speed VCSELs featuring strained InGaAs quantum wells.

In order to avoid the complicated phase with height mapping relationship calibration and phase unwrapping process of traditional 3D surface measurement methods, a three-dimensional surface measurement method based on deep learning was proposed. By sampling the rotating fringe pattern, data samples of different directions of the object to be measured are obtained as the training set. After the model is trained well, the mapping relationship between the deformed fringe pattern and the height of the measured object can be directly obtained to realize the 3D surface shape measurement of the object to be measured. The computer simulation and experiment show that the method is effective.

Recently, free-space optical neural networks (ONNs) have gained extensive interest as emerging machine learning platforms for implementing artificial intelligence tasks, such as image classification. Despite various optical implementations of electronic neural networks (ENNs), the bulky volume of optical components remains challenging to deploy edge devices, such as Internet of Things peripherals, wearable devices, and camera. To address this problem, we propose a compact lensless optoelectronic convolutional neural network (LOE-CNN) architecture with a lensless optical analog processor utilizing a single optimized diffractive phase mask (DPM) to perform convolution operations without Fourier lens. Comparing the processor with a commercially available NVIDIA A100 Tensor Core GPU in terms of speed and power, indicates the optical computing platform enables to replace the electronic processor in latency reduction and energy savings. Furthermore, we compare the LOE-CNN with two all-electronic neural networks (i.e., fully connected neural network [FC-NN] and convolutional neural network [CNN]) over the Modified National Institute of Standards and Technology (MNIST) dataset and Fashion-MNIST dataset, respectively, and demonstrate that the LOE-CNN can be functionally comparable to existing electronic counterparts in classification performance. My study not only opens up new application prospects for free-space ONNs based on compact lensless single-chip convolution processor, but also facilitates the development of ONNs-based smart devices.

In this paper, a novel 1×2 MMI coupler is proposed in the 3 m thick-silicon platform, which is based on rib input/output waveguide and strip multimode core waveguide. The hybrid waveguide structure can achieve a low-loss optical transmission with 0.017 dB at 1550 nm which is a comparable performance of traditional strip MMI coupler. In addition, the proposed structure can directly join the power splitter with other optical element such as ultra-low-loss single-mode rib waveguide and high-speed electro-optical Mach-Zehnder interferometers, which is a strong candidate for the conventional waveguide transformer between strip coupler and rib modulator.

Existing particle size analysis methods are difficult to detect micron and submicron sized particles in transformer oil which generated during the early stages of transformer oil aging. As a supplement to the existing analysis methods, we introduce dynamic light scattering (DLS) to extended the lower limit of particle size detection to the nanoscale. In this work, we designed a novel multi-angle DLS system which utilizes optical fibers and microfluidic chips to achieve accurate measurement in high viscosity media. We use the self-developed system to analyze the particle size distribution in multiple aging transformer oil samples, the experimental results show that the relative errors of measurement for simulated aging samples are within 7%, and the measurement results for real aging samples are consistent with the microscopic observations.

In this paper, the simple multi-band triangular frequency modulation (TFM) signals generation with multiplying bandwidth and center frequency using photon-photon resonance (PPR) effect in three-section monolithic integrated directly-modulated laser (TS_MIDML) has been experimentally demonstrated. The traditional optical-injection system replaced by the TS_MIDML, and the high-speed external modulator, polarization controller and filter are eliminated in this paper. A three-band TFM signals with carrier frequencies ranging from X-band to K-band are given as an example, and the time bandwidth product (TBWP) up to 20000. The numbers of bands and TBWP of generated signals could be easily adjusted by tuning the reference signal from arbitrary waveform generator (AWG). The results of auto-correlations of the generated waveforms are also given.

Aiming at the sensitivity of Raman anti-Stokes scattered light to the temperature, a novel distributed optical fiber temperature measurement system based on automatic power correction algorithm is proposed and experimentally demonstrated. The power automatic correction algorithm is based on corresponding temperature data and power value of the scattering position for temperature calibration. And by the power and temperature conversion relationship of the Raman anti-Stokes scattering light, the measured Raman anti-Stokes optical time domain reflecting trace for temperature demodulation is corrected by the obtained power correction coefficient. Therefore, the influence of unfavorable factors in traditional single-channel and double-channel Raman optical fiber distributed temperature demodulation methods are eliminated, so that the stability and measurement accuracy of the temperature measurement system is improved. The experimental system is set up with multimode fiber (MMF) in a range of about 16.3km, and the experimental results achieved the spatial resolution of 2m and the temperature measurement accuracy of ±1.6℃, and the response time is less than 1.5s, which is of great significance to practical engineering application.

Holographic optical element (HOE) have been widely applied in many fields. However, the fixed focal length limits its application in dynamic optical systems. The existing methods have the problems of limited adjustment distance and difficulty in correcting the aberration during the adjustment. This paper proposes a method that can correct the aberration while adjusting the HOE focal length in a large range. This method modulates the illumination wave front by superposing the modulation phase factor to achieve the change of the reconstruction distance, that is, the change of the focal length of the HOE. To design modulation phase factors corresponding to different focal lengths, the relationship between the parameters of the modulation phase factor and the focal length of HOE was derived based on the Fresnel diffraction integral formula. To solve the problem of the aberration cannot be uniformly compensated at different focal length, aberrations of different types, sources, and reconstruction distances are compensated separately. The method proposed in this paper achieves a wide range of adjustment of HOE focal length and correction of aberration during the adjustment process. In the experiment, the focal length of HOE is adjusted to 30cm, 40cm, and 50cm, and the evaluation functions of aberrations have changed towards the direction of aberration reduction. This method can be used for the design and fabrication of adjustable HOE, which is expected to be used in holographic projection, structured light generation and many other fields.

The detection and imaging of the microvascular map play a vital role in providing valuable pathological evidence for a variety of physiological disorders. Optical coherence tomography angiography (OCTA) is a non-invasive technique that allows high-speed, high-resolution visualization of microvascular networks without the need for contrast agents and invasive manipulation. In this study, we developed a fiber-based polarization-sensitive optical coherence tomography (PS-OCT) system that utilizes a 200 kHz swept source at 1310 nm. To reduce phase artifacts and provide excellent motion contrast for vascular imaging, we have incorporated the complex correlated phase gradient variance (CCPGV) method. Additionally, to address the challenges posed by birefringence dispersion, we implemented a dual-state numerical dispersion compensation method. By imaging human skin, we have successfully demonstrated the effectiveness of our system in visualizing the vascular map while minimizing noise interference. The high-quality imaging and accurate visualization of vascular networks provided by our system hold significant potential in enhancing the understanding and assessment of various pathological conditions. This can benefit both researchers and clinicians in their biomedical investigations and patient care.

The Mueller matrix encompasses polarization information, correlated with microstructure and optical properties. However, coupling effects complicate the retrieval of anisotropy source values. To address this, we propose a novel approach of mapping the Mueller matrix onto the Poincaré sphere and introduce a set of Global-Polarization Stokes Ellipsoids (GPSE) parameters to potentially retrieve two primary anisotropic sources: cylinder scattering and birefringence. Using porcine skeletal muscle as the reference object, we establish a database of Mueller matrices and GPSE via Monte Carlo simulation and train regression models based on multi-layer perceptron (MLP). Experimental results demonstrate that GPSE achieves comparable or even better prediction performance for anisotropy numerical values compared to the Mueller matrix model, indicating that GPSE parameters effectively contain anisotropy information present in the Mueller matrix. With an intuitive expression form and sensitivity to anisotropy, GPSE holds great potential in retrieving the values of anisotropic sources in tissues.

The multiplexing of vortex beams carrying orthogonal orbital angular momentum (OAM) modes holds the potential to enhance the channel capacity (CC) of wireless optical communication systems. This paper proposes a method that utilizes optical phase conjugation (OPC) wavefront shaping by spatial light modulator (SLM), and regards the scattering medium diffuser (SMD) as an optical modulator to achieve the demultiplexing of multiplexed OAM beams through space channel. We also analyze the communication capability of the demultiplexing system in the atmospheric turbulence (AT) channel. In the proposed system, a simulation setup is employed where multiplexed OAM beams propagate through an AT channel simulated by a random phase screen. At the receiving end, the OPC method is used to obtain a phase mask that is loaded onto the SLM for wavefront shaping of the input multiplexed OAM light. The light field is then modulated through the SMD's multi-scattering effect, enabling the separation of multiplexed OAM beams to distinct detection positions for demultiplexing. This paper investigates the influence of the OAM mode and AT strength on the focusing of single-mode OAM beams. Additionally, it examines the impact of OAM multiplexing combinations, AT strength, and transmission distance on the detection probability, bit error rate (BER), and CC. The results demonstrate the effectiveness of the demultiplexing system in mitigating mode expansion caused by AT, offering valuable insights for the design of robust OAM multiplexing systems.

In order to satisfy the sensing requirement for low-concentration or even trace detection using Terahertz (THz) spectroscopy, a new metamaterial sensor (MS) based on a double-opening elliptical ring array is designed by electromagnetic simulations. After optimization of the MS structure, the proposed MS has a strong resonant peak absorption peak around 2.853 THz and is entitled with high-Q and high-sensitivity simultaneously. The Q-value of the designed MS can reach to 385.0 and the sensitivity can reach to 371.5 GHz/RIU for a dielectric analyte with a thickness of 30 μm and it still can remain 40.0 GHz/RIU for a very thin analyte with a thickness of 1 μm. These results indicate that the designed MS has good sensing performance and can potentially be applied to high-sensitive detection of low-concentration or even trace samples.

Underwater optical images are affected by light attenuation, scattering, noise, etc., resulting in low image quality. Therefore, it is extremely significant to improve image quality and optimize network detection performance for underwater target detection. In this work, a YOLOv8-based underwater target detection method via image enhancement is provided, making full utilization of its advantages in large-scale feature learning. To address the issue of insufficient detection accuracy of the YOLOv8 algorithm on the original optical underwater target dataset, we employ an image fusion-based image enhancement method to improve underwater optical image quality. Combining different weights and scales, this method fuses multiple enhanced images to eliminate scattering and color bias, which enhances target features significantly. The results illustrate that the designed YOLOv8-based algorithm via image enhancement improves the precision by 20.5% and exhibits better performance in small, multiple and overlapping targets scenarios, where this algorithm gives a promising way for underwater optics target detection.

Infrared and visible image fusion technology aims to integrate the radiation information of infrared images and the details of visible images into one image, which is widely used in video surveillance, target tracking etc.. Thereinto, maritime surveillance often uses infrared and visible images to monitor ships. With the rapid development of deep learning technology, numerous image fusion algorithms have sprung up. However, maritime images can be affected by extreme illumination conditions during fused. Note that the quality of maritime images is extremely significant for identifying ship targets. Therefore, the quality of fused image is necessary for further investigation. Here, a progressive image fusion network with a lighting awareness module, named PIAFusion, is provided for maritime images fusion. Contributed by the light sensing subnetwork, PIAFusion can adaptively fuse the common information and complementary information of images. Evaluated with five operators in daytime and night cases, the results demonstrate that this method significantly improve the fused image quality, compared to common fusion methods (i.e., GTF and DenseFuse). In addition, this method preserves more details of the source image. The progressive fusion network illustrates better fusion performance for maritime images in different lighting cases.

The optical images quality in dark underwater background is usually degraded, influencing the results of accurate identification, terrain mapping and seabed exploration. Thus, the super-resolution methods for dark underwater optical images attract extensive research interest. In this work, the SwinIR model is provided for dark underwater optical images super-resolution. Here, the EUVP DARK dataset with dark underwater background is employed, which clusters 5500 paired images. The SwinIR networks has high speed of process with large-size image capability and plentiful image detail. Compared with the traditional SRGAN method, the super-resolution reconstruction speed increases about 18.3%, and the peak pignal-to-noise ratio (PSNR) and structural similarity (SSIM) of SwinIR test results on the EUVP DARK dataset increase by 14.4% and 15.8% respectively, the results illustrate that our method improving the accuracy and quality of reconstruction. In conclusion, the hierarchical structure of SwinIR and self-attention mechanism adaptive attention weights in generated to the image, enabling precise adjustment and control of detail and texture. This method provides an efficient approach to dark underwater image quality enhancement.

With the principle of electrically controlled birefringence (ECB), we propose a new method to spatially separate the azimuthally and radially polarized beams. The method is premised on a regularized arrangement of liquid-crystal (LC) induced by sparse polymer ribbons.The ECB effect was achieved by a hole-patterned LC device with an initial radial alignment, which is induced by polymer ribbons pre-fabricated on the substrate. The polymer ribbons were formed on the substrate via the ultraviolet (UV) mask exposure method, which has the advantages of low cost, simple fabrication process and can be used for mass production. When the voltage signals are applied to the fabricated LC device, a gradient refractive index distribution will form inside the device. Restricted by the inherent polarization-sensitive properties of the nematic phase, it corresponds to the extraordinary optical component, which is exactly the radially polarized beam. According to the above principle, the extraordinary and ordinary polarized components can be separated. Experiments demonstrated that the spatial separation was effectively achieved by the proposed LC device. The proposed method has provided an approach for the light field manipulation based on patterned liquid crystal alignment.

This paper investigates the scattering properties of a uniaxial anisotropic coated (UAC) sphere that is irradiated by two focused Gaussian beams with arbitrary directions using the generalized Lorenz-Mie theory (GLMT). We derive the dual Gaussian beam expression by utilizing the orthogonality of spherical vector wave functions (SVWFs). The SVWFs are employed to expand the electromagnetic fields within each region of the coated sphere, combined with the boundary conditions, and the scattering coefficients and the radar cross-section (RCS) for the scattering of UAC sphere irradiated by two Gaussian beams are obtained. We present numerical simulations of the angular distribution of the RCS. The effects of the waist width, the incident angle and the particle inner diameter on scattering intensity are analyzed. The findings demonstrate that when the particles are illuminated by two beams of light at varying incident angles, the E-plane RCS will attain its maximum value in the corresponding incident direction. Remarkably, when the two beams of light propagate in opposite directions, the angular distribution of RCS exhibits symmetrical shapes, and the H-plane RCS attain minimal value at ±90°. As the waist width increases, the RCS also increases, albeit with different increments at different angles. As the particle's inner radius expands, the RCS around 0° and 180° gradually increases, while exhibiting oscillations around ±90°. The theory and numerical analysis provide beneficial help for laser detection, scattering and optical manipulate of coating particles.

In order to reduce the active region temperature of single core semiconductor lasers and improve the reliability of packaging devices, based on the COS packaging form, this work conducted heat dissipation analysis on the established "sandwich" structure and composite stacked structure semiconductor laser models. The flip chip packaging structure was optimized, Graphene film was used to increase the transverse heat dissipation channel of semiconductor laser, and the longitudinal heat conduction was carried out in combination with the heat dissipation copper sheet. Finally, the structural model of Graphene composite heat sink was established using SolidWorks software. By using ANSYS finite element software for steady-state thermal analysis comparison, the goal of reducing the temperature and thermal stress in the active region of semiconductor lasers was achieved. The proposed composite heat sink model can provide a design idea and method for high reliability laser packaging structures.

Waveguide-coupled germanium-on-silicon photodetectors have garnered significant attention due to the sensitive infrared response of germanium and compatibility with CMOS technology, widely employed in high-density and large-scale integrated optoelectronic products. These inherent advantages have also led to the huge interest in germanium-on-silicon single photon diodes. In this paper, we present the design of a microring resonator enhanced germanium-on-silicon single photon avalanche diode. The microring resonator is designed to enhance the light absorption in germanium absorption region through resonant enhancement. Moreover, a three-terminals structure is implemented to mitigate the dark count rate. And by optimizing the doping concentration and width of the doping region, the electric field at the silicon-germanium interface is effectively suppressed, resulting in a significant reduction in dark current. We employ a 2D Monte Carlo simulator to obtain the photon detection efficiency. This microring resonator enhanced single photon avalanche diode demonstrates twice the photon detection efficiency compared to the same size straight waveguide detector. In conclusion, our designed detector exhibits higher detection efficiency and lower dark current compared to conventional devices. These results illustrate clear potential for integration with Si photonics for on-chip applications.

Photonic random demodulator (RD) is a widely studied scheme to realize photonics-assisted compressive sensing (CS). Since CS via an RD requires a pseudo-random binary sequence (PRBS) bit rate that is at least twice the signal’s Nyquist rate, the generation of the ideal PRBS in practical systems requires a very large signal bandwidth and is difficult to achieve, leading to poor mixing results from the RD and limited performance of the photonics-assisted CS system. To solve this problem, in this work, we propose a method to compensate for the poor mixing results by using a complementary PRBS and a parallel optical path, thus achieving better CS results in the case of limited PRBS bandwidth. The feasibility of the proposed method is verified by simulation. When only a 4-Gbps PRBS with a bandwidth limited to 0 to 6 GHz is used and the signal to be sampled is a multi-tone signal lower than 1.6 GHz, it is difficult to reconstruct the multi-tone signal or the quality of the reconstructed signal is poor when the starting point is randomly selected for downsampling due to the non-ideal PRBS. When the complementary PRBS is also limited to 0 to 6 GHz, the quality of the reconstructed signal is also improved in most cases. The method proposed in this work provides a good solution for the realization of CS using photonics-assisted RD in real systems, which can reduce the influence of non-ideal PRBS on signal recovery without expanding the bandwidth of the used PRBS.

In recent years, due to harsh working environments, increased accuracy requirements, and limited fiber optic technology levels, the active all-fiber optical current transformer (FOCT) used in the power grid of China State Grid is equipped with optical power compensation modules and modulation voltage compensation modules. However, aging of the light source (10 years) and extremely low temperature (-40℃) can cause the compensation modules to fail, resulting in decreased measurement reliability and significant losses to the power grid system. In this paper, by simulating the working status of FOCT when the power source ages and the modulator function deteriorates, it is found that the second harmonic and phase modulation depth are parameters that can timely reflect the working status of the optical power compensation module and the modulation voltage compensation module. This provides reference for the monitoring of feedback FOCT and helps improve the stability of feedback FOCT.

Optical frequency combs are increasingly being adopted in various measurement applications. However, the sensitivity of free-running optical frequency combs and the large size and complex connections required for locking equipment pose significant obstacles to their on-site application. To address these challenges, we present an integrated optical frequency comb repetition rate locking control system that greatly reduces the volume of the locking system.In this system, we firstly control the temperature of the resonator cavity to achieve a wide range of control over the effective length of the cavity. A temperature control box for the resonator cavity is designed, incorporating semiconductor cooling chips to regulate the temperature. Secondly, we employ piezoelectric ceramics to achieve small-scale stretching control of the resonator cavity length. These control methods work in synergy to achieve high-quality repetition rate locking. The use of a loop filter in the system establishes the dynamic performance of the repetition rate locking loop and effectively suppresses the high-frequency components of the phase discriminator output. Through testing of the research system, the temperature control system demonstrates a temperature control range of 20-40°C, with a temperature control accuracy of ±0.01°C. With the assistance of the temperature control system, the repetition rate locking system achieves a repetition rate locking duration of over 10 hours, with a fluctuation range of less than 5 mHz, an Allan deviation of 217 μHz@gate 1s, and a relative frequency stability of 3.89E-12.This system successfully achieves high-frequency stability and long-term locking of the optical frequency comb's repetition rate.

In this work, we propose and experimentally demonstrate an improved cylindrical liquid crystal (LC) lens that allows for lateral shifting of the optical axis by use of a simple electrode design. The proposed cylindrical LC lens has potential applications in various fields, such as light sheet imaging, beam shaping, 3D displays, and laser scanning. The lens is composed of two substrates with comb-type electrodes of equal width on their inner surfaces. The comb-type electrodes are arranged in parallel and aligned with each other. Each comb-type electrode is applied with two driving voltages, generating a parabolic and a linear voltage distribution respectively. The voltage difference (VD) between two electrodes contains a quadratic and a linear term, so the symmetrical axis of VD can be shifted by adjusting the four driving voltages. By controlling the VD across the aperture within the linear response region of the LC material, the parabolic VD generates a parabolic phase profile, and the optical axis shifts as the symmetrical axis of VD shifts. The driving method of four voltages to adjust the optical power and the position of the optical axis is described in detail. The combtype electrodes are developed using a standard photolithography process, and a cylindrical LC lens with an aperture width of 2 mm and LC layer of 50 μm is prepared. The results demonstrate that the optical axis can be shifted in the aperture with high precision while maintaining near-ideal phase profiles.

To control the laser parameters and meet the requirements of precise physical experiments, it is necessary to accurately obtain the spectral width of the frequency-modulated (FM) light. The FM light has complex comb distribution that the morphological characteristics are different from the typical continuous spectrum. In this paper, we define the spectral width of the FM pulse according to the nature of the phase modulation and develop a correlation traversal algorithm based on spectral morphology matching. Then, we establish the relationship between the measured spectrum of the medium-precision spectrometer and the simulated spectrum and complete the spectral width calibration. The correlation of the measured spectrum and the simulated spectrum in 2.5 GHz frequency modulation, within the spectral width range of 0.05 nm ~ 0.30 nm is calculated. The correlation traversal algorithm can obtain a strongly correlated theoretical spectrum with an R-value greater than 0.9 for any measured spectrum. Through linear fitting of all data, we obtain the relationship curve between the -3dB spectral width measured by the medium-precision spectrometer and the calibrated spectral width. And the determination coefficient of the relationship curve is 0.9989. The results show that the spectral width calibration method has the advantages of strong correlation and high linearity. The spectral width calibration method completes the spectral width calibration of FM light for the first time, which lays a foundation for precise control of spectral parameters in inertial confinement fusion precision physics experiments.

Neuromorphic computing system inspired by the human brain has the capability of breaking through the von Neumann bottleneck, which can improve the efficiency of data processing. To deploy efficient neuromorphic systems, the development of synaptic devices is imperative. However, achieving tunable synaptic behaviors in a single transistor remains challenging. In this work, a silicon nanowire-based photoelectronic synaptic transistor is developed to achieve tunable synaptic behaviors. Using the floating-body effect and a cylindrical surrounding double-gate (CSDG) structure, we simulated excitatory and inhibitory synaptic plasticity in a single device. Additionally, our device also simulated various synaptic characteristics by modulating the bias voltages and light pulses, such as excitatory and inhibitory postsynaptic current (PSC), short-term potentiation (STP), short-term depression (STD), long-term potentiation (LTP), and forgetting behavior. This study provides an effective strategy for developing tunable photoelectronic synapses. Furthermore, Si processing compatibility also makes the synaptic device a promising contender for the implementation of neuromorphic computing.

The measurement of ultra-weak magnetic fields relies on the conversion of magnetic field information to atom spins using alkali metals. In this context, the detection of magnetic fields is accomplished through rotation angle measurement of linearly polarized light. This paper proposes a novel method to suppress mechanical errors between polarizers in the rotation angle measurement, taking advantage of the optical setup characteristics in atomic magnetometers. The method involves applying two separate frequency modulations to the pump beam and probe beam, effectively eliminating mechanical errors between the polarizers as a direct current component using a double-channel lock-in amplifier. Additionally, the double modulation method offers a solution to suppress shot noise caused by incident beam fluctuations or transverse spin relaxation, as well as mechanical errors among optical elements in the light path, enabling high-precision measurements.

Full-color display has always been a research focus and technical difficulty in the field of display. One of the current research hotspots is the use of color conversion layer (CCL) technology to achieve full-color display. Ultraviolet or blue LEDs can be converted by CCL to achieve full-color pixel display. Compared with traditional technologies, this technology does not require steps such as mass transfer. This method greatly simplifies the processing of full-color display. In this paper, we propose a method to achieve two-color patterned display of perovskite thin films by laser direct writing technology. The laser acts on the perovskite quantum dot thin film covered by the polymer film to form pattern or array based on photo-quench. Then other color perovskite quantum dot solutions is spin-coated. At last, the upper quantum dot film is washed off with solvent. Due to the protective effect of the polymer film, the coexistence of two-color quantum dots is realized. This method not only broadens the application of quantum dots in display, but also provides a new idea for the subsequent laser direct writing technology to realize multi-color or even full-color display.

A no mode hopping and narrow linewidth external-cavity wavelength-swept laser (EC-WSL) based on a traditional Littman-Metcalf structure is proposed and experimentally demonstrated. The wavelength scanning output range of the proposed laser without mode hopping is from 1520.82 nm to 1579.95 nm (namely, 59.13 nm). The narrow spectral linewidth less than 100 kHz is simultaneously realized. Meanwhile, the output power of the presented laser exceeding 14.8 dBm over the entire wavelength scanning range is obtained. In view of the good tuning characteristics, we achieved now, the proposed EC-WSL may be used in practical engineering fields such as gas detection.

In this work, an all-fiber high-power cascaded master-oscillator power amplifier (MOPA) system emitting frequency-stabilized single-frequency laser pulses at 1550 nm is presented. An external cavity laser diode with a narrow linewidth of 5 kHz is used as the seed source. Owing to the use of frequency locking components and a matched closed-loop system, the seed source has stable output frequency and power. The on-off extinction ratio of 80 dB is achieved by using digital and analog acousto-optic modulators in series. Then the seed laser is amplified by a three-stage cascaded all-fiber amplifier consisting of two pre-amplifiers and one main amplifier. The MOPA system delivers 200-ns laser pulses with a peak power of 800 W at a repetition rate of 10 kHz. The output laser has an operating linewidth close to the transform-limited. The polarization-extinction ratio is 20 dB, and the optical signal-to-noise ratio is higher than 45 dB. The monolithic all-fiber Erbium-Ytterbium co-doped pulsed fiber amplifier can be used as the high-energy radar transmitter of compact long-distance coherent Doppler lidar systems.

High-power lasers operating at the E- and S-bands that overlaps with the strong absorption band of water molecules have been exploited for applications such as medical diagnoses, laser therapy and lipolysis. This type of lasers can be realized with a MOPA (master oscillator power amplifier) configuration, consisting of a seed laser and a fiber amplifier, which allows one to achieve easily boosting the output power. However, the efficient fiber amplifiers operating in the E- and Sbands using most rare-earth-doped silica fibers is inaccessible. In contrary, the optical fibers doped with bismuth (Bi) capable of providing broadband amplification from 1100 to 1800 nm can be utilized to build a desired fiber amplifier. In this work, we demonstrated the output characteristics of developed amplifiers based on a Bi-doped 5GeO2 − 95SiO2 fiber (BGSF) drawn from a preform fabricated by the modified chemical vapour deposition (MCVD) technique. The corepumped fiber amplifiers are characterized by a small-signal gain of >20 dB at a wavelength of ~1440 to 1450 nm and the noise figure of ~4.5 to 6 dB. In addition, the fiber amplifier was employed to amplify a signal from a tunable continuous wave laser from 1390 to 1510 nm. This work presents the significance of Bi-doped fibers to build a fiber amplifier across E- and S-bands which could be attractive for medical diagnoses and laser therapy applications.

Fused silica is widely used in aerospace and precision integrated micro-optical sensors due to its high hardness, low coefficient of thermal expansion, high transmittance properties and high chemical stability in harsh environments. Due to the amorphous characteristics, fused silica wet etching is isotropic and cannot realize specific structural functional devices; dry etching process is complex, costly, and relatively low productivity. These characteristics make the processing of fused silica extremely difficult, with high cost and low yield. Femtosecond laser processing has been widely used in the processing of complex and fine three-dimensional structure of fused silica due to its wide adaptability of materials, high degree of processing fineness and non-mask processing technology, but the surface of the processed surface is relatively rough. Fine micro-optical devices can be realized by wet-assisted femtosecond laser processing. In this study, microstructural patterns were fabricated on fused silica using a tightly focused femtosecond laser by means of a self-developed ultrafast laser processing instrumentation. By controlling the laser processing parameters and the etching time of HF solution to realize the precise modulation of linewidth, period and height of the grating, one/two dimensional gratings, and the Fresnel zone plates with circular and elliptical focal points and the biomimetic compound eye microlens array were successfully fabricated. Finally, the performance of the fabricated optical components were characterized, which were comparable to theoretical simulation values. The results show that the total diffraction efficiency of the fused silica gratings fabricated using this method reaches 85.5%; the Fresnel zone plates and the bionic compound eye microlens array have good focusing effects. This study provides a reference method for the fine micromachining of hard materials such as fused silica, and provides a theoretical basis for its engineering application.

To manipulate on-chip mid-IR signals, it is pivotal to construct a waveguide with subwavelength energy confinement. However, a deep subwavelength optical waveguide always suffers from high signal crosstalk, resulting in an inevitable coupling loss of multi-channel communication. To solve this problem, in this paper, a mid-IR hybrid waveguide which is composed of a graphene/hexagonal boron nitride (hBN) structure and a dielectric waveguide, is designed to realize a strongly enhanced light-matter interaction, accompanied by a low crosstalk transmission. The surface-phonon-plasmon-polariton mode generated by the graphene-hBN is coupled to a nanowire dielectric mode to form a hybrid guiding mode. Benefiting from this hybrid mode, the results show that it is possible to minimize the crosstalk of two parallel waveguides by reducing the width of the graphene-hexagonal hBN structure even if the waveguide separation length is at the nanoscale, thereby enabling low crosstalk optical transmission. Our designed approach opens the door for possible uses in nanophotonic devices such as amplitude equalizers, mode multiplexers, and wavelength-selective switches in optical communication systems.

The composite materials are widely used in the aerospace field due to their satisfying properties. However, the structural damage always appears at the manufacturing stage, and various defects are also produced during the service process. Ultrasonic detection is the most popular approach for Non-Destructive Testing, but challenges still exist in composite materials for their large acoustic attenuation and mechanical physical anisotropy. Herein, as an alternative to the conventional electric transducers, we propose a new optical ultrasonic sensor for the defect detection of aircraft composite structures. The sensor utilizes a ceramic ferrule to construct a low-fitness in-line interferometer. Thermoplastic polyurethane elastomer rubber (TPU) is employed as the sensitive film and a single mode fiber grating is involved into the optical interferometer to improve its visibility. The sensor response and stability are characterized in experiments, and the artificial defects in a honeycomb-like plate are identified in time/frequency domains. Owing to the high elasticity and good durability of TPU, the proposed sensor possesses excellent performance of high sensitivity and reliability for detecting weak echoes in harsh conditions.

A polarization-insensitive four-channel wavelength-division multiplexing (WDM) (de)multiplexer based on Mach-Zehnder interferometers is proposed and demonstrated. Polarization insensitivity can be achieved by utilizing the square waveguides and bend directional couplers (bend DCs) based on silicon oxynitride (SiON) waveguides. The WDM (de)multiplexer has an 800GHz spacing for LAN-WDM application. Two stages of cascaded MZIs are utilized to achieve a four-channel spectral response. For the realized WDM (de)multiplexer with Gaussian-like passbands, the polarization-dependent losses (PDL) are less than 0.7dB for all 1-dB passbands. The insertion losses are <~ 3dB and the crosstalk is <~ -12dB for both TE and TM polarizations at channel central wavelengths.

Gallium-based liquid metals (LMs), including elemental gallium and associated alloy metals, are notable for their liquid state at room temperature. These LMs have gained attention due to their safety, non-toxicity, and exceptional physical and chemical properties. They exhibit optical resonance in the UV-VIS-IR spectral range, making them potential alternatives to expensive precious metals like gold and silver. However, the optical properties of gallium-based LMs have not been fully explored, especially their photoacoustic property. Photoacoustic detection is a label free method based on photoacoustic effect, detecting the optical absorption contrast of samples through photoacoustic waves. Photoacoustic detection has the advantages of non-contact, highs sensitivity, good contrast and etc. Using the photoacoustic detection method, we can avoid the influence of light scattering on the metal surface and thus obtain the optical absorption of gallium-based LMs directly. In this paper, we report a photoacoustic detection system based on intensity modulated high repetition supercontinuum laser to explore the light absorption properties of EGaIn LM.

Bilayer molybdenum ditelluride (MoTe₂) exhibits promising research potential in silicon-based optoelectronics due to its near-infrared emission band. Although previous studies have shown that the direct and indirect bandgaps are closely located, the origin of the dominant exciton in photoluminescence (PL) emission and the energy difference between the direct and indirect bandgaps remain uncertain. To address these issues, we performed comprehensive micro-PL and absorption measurements on monolayer and bilayer samples, incorporating electrical control, across a wide temperature range of 4 to 300 K. These systematic measurements determined that the dominant PL emission in bilayer MoTe₂ arises from an intralayer exciton with a direct bandgap and the energy difference between the direct and indirect bandgaps in the bubble-strained bilayer sample with a strain of approximately 1% was estimated to be around 10 meV in experiment, consistent with theoretical calculations in the literature.

3D convolution based stereo matching network has a wide range of research prospects at present, such as 3D measurement, unmanned driving, etc., but there is still room for improvement in accuracy. This paper proposes a threedimensional matching method based on deep learning: In the feature extraction part, a multi-layer learning parameter guiding feature fusion module is proposed, which can preserve the pixel gradient of the edge when sampling under single channel image guide. Then, the instance whitening noise of the output feature map is calculated, which effectively eliminates image pixel shift and feature similarity through the covariance threshold. In addition to using the traditional SmoothL1 loss function, the algorithm calculates the stereo focus loss by designing the confidence detection network to adjust the cost volume. The algorithm is tested on SceneFlow and Kitti series datasets. Using a multi-layer guiding module, instance bleaching loss, and stereo focus loss simultaneously compared to the original version, the error between test result and Ground Truth in the first frame (D1 Loss) of are reduced by 30.6%(Kitti2015), and the three-pixel error (3PE) is reduced by 6.3%(Kitti2012), which verifies the effectiveness of the algorithm.

Wavefront shaping technique has been applied to actively control the intensity profile of optical speckles, and a recent progress is to realize glare suppression with the low-transmittance eigenchannels of the transmission matrices (TMs). This makes it possible to custom-tailor the speckle fields. For the purpose of suppressing glare at will, research about the properties of low-transmittance eigenchannels in glare suppression is demanded. In this paper, we report the area expansion effect of glare suppression with low-transmittance eigenchannels. With numerical simulations, we found the actual darkened area was larger than the set target area due to the transverse correlation of the speckle field. Their difference is related to the measuring noise of the TM and gets smaller with the increase of the noise intensity. We believe our research could help to design structured speckle fields, and it will be of significant for advanced applications of optical speckles.

In this paper, an optical solar reflector (OSR) composed of an aluminum-doped zinc oxide (AZO) metasurface, a dielectric layer (SiO₂), and a reflective layer (metal layer) was designed based on Kirchhoff’s law, which combined high solar spectral reflection with high thermal mid-infrared emission performance. The effects of structural unit length, period, thickness, and dielectric layer thickness of the AZO metasurface on the solar spectral reflection and thermal mid-infrared emission (absorption) performance of the OSR were calculated and analyzed by using the time-domain finite-difference method, and a structural model of localized surface plasmon polariton (LSPP) based on broadband infrared enhanced absorption was established. The results show that the metal reflective layer material is Ag, and the OSR achieves the best absorption performance structure when the structural unit length L of the AZO metasurface is 1.1 μm; thickness h1 is 0.04 μm; period d is 1.3 μm, and SiO₂ medium thickness h2 is 1.4 μm. The designed OSR model has two absorption peaks reaching 99% in the range of 2.5–20 μm and absorption rates greater than 80% in the range of 5.0–8.3 μm and 10.2–15.9μm. The top square resonant unit makes the OSR independent of polarization and angle. The results provide a new idea to further improve the absorption rate of OSRs based on broadband absorption.

In the field of computer vision such as target detection and 3D positioning, point cloud registration has always been one of the key problems, which requires alignment two point clouds through rigid spatial transformation, accuracy, robustness, speed and other factors. Point cloud registration based on deep learning has received a lot of research in recent years. Compared with the conventional methods, They show a great advantage in their registration performance, To improve the performance of deep learning on point-cloud registration, This paper uses Kernel correlation to compute and store the neighborhood information of point clouds, While extracting local geometric features by convolutional neural network and Offset_Attention module aggregation, Then use Singular value decomposition SVD to predict the final rigid transformation matrix, and finally achieve high-quality registration. In this paper, by training our model on the ModelNet40 dataset, And the source and target point cloud are sampled independently, And also extract the non-axisymmetric targets for additional tests, Achievalized a more equitable registration network experiment, the Root-mean-square deviation (RMSE) is 12.58% higher than before, which verifies the effectiveness of our network.

In recent years, photoacoustic imaging has become a new non-destructive medical imaging technology. In this paper, a photoacoustic imaging technology for human bladder cancer was proposed, which combined transurethral endoscopic photoacoustic excitation in bladder cavity with a transrectal photoacoustic signal detection. By establishing a three-dimensional( 3D) optical model of bladder tissue, the distribution of light energy deposition in the bladder tissue was obtained through the 3D Monte Carlo method. The velocity potential was used to calculate the photoacoustic signal, and the scanning photoacoustic image of bladder tissue was reconstructed. The results showed that the proposed photoacoustic imaging technique with transurethral photoacoustic excitation in bladder cavity was expected to detect early bladder cancer nondestructively.

The mid-infrared (MIR) band encompasses crucial molecular fingerprint regions and atmospheric infrared windows, making it highly significant for various applications such as environmental monitoring, biosensing, and medical diagnostics. In this study, we present the fabrication of a MIR microlens array (MLA) using a combination of highspeed femtosecond laser scanning technology and thermal imprinting technology. The resulting microscale convex MLAs were densely packed, with over one million units on a 2cm×2cm chalcogenide glass (CHG) surface, offering adjustable sizes and non-spherical contour profiles. The CHG MLAs demonstrated exceptional imaging performance, achieving a high transmittance of 60-70% within the 2.5 ~ 15μm range. This technique boasts advantages such as low cost and high efficiency, presenting significant potential for widespread applications in the forefront of the mid-infrared field.

Accurate measurement of photosensitizer concentration in real-time in vivo bladder tissue was beneficial for improving the effectiveness of photodynamic therapy and achieving precise treatment of bladder tumor. In this paper, the potential ability of a transurethral photoacoustic imaging technique in visualizing and monitoring the photosensitizer concentration in the photodynamic therapy of bladder was evaluated. A bladder tissue optical model was established, and 3D Monte Carlo light transport method was coupled to calculate the photoacoustic signal. Photoacoustic signals in different photosensitizer concentrations were recorded. Results illustrated that a clear linearity between the photoacoustic signal intensity and photosensitizer concentration can be observed. It revealed that the proposed transurethral photoacoustic imaging technique has the potential to estimate in vivo photosensitizer concentrations and to guide laser-induced photodynamic therapy of bladder tumor.

In recent years, research interest has rapidly increased in the selective metallization of different substrate materials (flexible substrates and hard and brittle materials). Due to their unique optical and electrical properties, the fabrication of metal patterns on various substrate materials has a wide range of applications. These include micro-electro-mechanical systems, micro-heaters in micro-fluidic systems, electrodes for electronic devices and flexible wearable devices. However, the differences in the properties of the substrate materials themselves lead to poor adhesion of the metal micropatterns to their substrate materials, which is one of the main factors affecting the selective metallization of their surfaces. Therefore, a method for selective preparation of high-performance patterning is needed. Laser direct writing technology, as an emerging low-cost, high-efficiency and high-precision processing technology, can realize the preparation of fine metal selective patterning. This is significant for preparing optoelectronics and semiconductor micro/nanostructures and devices. This paper reviews the research progress related to the preparation of highperformance Cu metal micropatterning by laser direct writing, which mainly includes laser direct structuring, laserinduced selective activation, laser-induced selective reductive sintering of metal precursor nano-inks and laser-induced forward transfer. By reviewing the research of this group and the current related research results, the current research status of the preparation of selective metal patterning in different substrate materials is investigated and introduced from the fundamental mechanisms and process characteristics of the various methods. This paper can provide a reference for the research and application of high-performance Cu metal micropatterning prepared by laser direct writing. These high-performance metal micropatterns are useful for microcircuit defect repair, glass heating devices, and transparent atomization devices, which could be a potential option for various microsystems.

Laser active suppressing jamming is one of the most effective technologies to cope with electro-optical imaging system. In order to obtain the exact assessment of laser jamming effect, we must acquire the laser jamming effect image. We proposed two methods for simulation implementation of laser jamming effect image in this paper, which were respectively based on theoretical model and measured data. First of all, the implementation flows of two methods were introduced. Secondly, we successively finished the simulation of laser jamming effect image according to the two flows. By comparing with the measured image, the significant correlation can be obtained with the method based on measured data, regardless of whether the jamming laser energy was high or low. The significant correlation can be achieved with the method based on theoretical model when the jamming laser energy was low. The research results can provide the technical reference for carrying out laser jamming experiment.

An approach to generating pulse trains with user-defined pulse positions in a phase-modulated optical frequency-shifting loop (OFSL) is proposed and experimentally demonstrated. In this method, the OFSL operates in the integer Talbot state, i.e., the repetition frequency of the driving waveform is equal to the free spectral range (FSR) of the OFSL. The phase of the optical field in the OFSL is manipulated by using an electro-optic phase modulator (PM) in each round trip. Then, pulses will be generated in the positions that the additional phase introduced by the PM is equal to an integer multiple of 2π in each round trip. Hence, the positions of the generated pulses can be controlled by designing the driving waveform. In the experiment, we firstly demonstrate the ability of the proposed scheme to control the pulse positions by applying four types of signals, namely, a linearly chirped waveform, a dual-chirp waveform, a quadratically chirped waveform, and a sinusoidal frequency-modulated waveform, to the PM. In addition, the proposed scheme can also be used to generate pulse trains with coded pulse positions. To verify this ability, two groups of coding sequences, i.e., “0101101110” and “1010010001,” are used to encode the pulse positions in a round-trip time of the OFSL. The proposed scheme can generate pulse trains with user-defined pulse positions, which can be used as a pseudo-random sampling source in compressed sensing (CS) systems.

The ultrasonic detection technology of railway locomotive wheels is of great significance to the safety of train operation. However, the current detection technology relies on experts ' manual operation, which has the disadvantages of low accuracy and high cost. In this paper, a detection method based on improved Exceeding YOLO Series in 2021 (YOLOX) is proposed. Firstly, a series of processing such as cutting and rotating the ultrasonic B-scan image obtained by LU system is carried out to obtain the B-scan data set of wheel ultrasonic defects after data enhancement. Secondly, we add an adaptive spatial feature fusion block (ASFF) to the tail of the Neck module of the YOLOX detection algorithm, and further improve the multi-scale feature map. Finally, the original BCEWithLogitsLoss in the loss function is replaced by FocalLoss to improve the ability to distinguish defects from similar backgrounds. The test results show that the detection rate of each type of the improved YOLOX model is more than 90 %, the false negative rate and false positive rate are less than 10 %, and the detection speed is 17 ms. Compared with the original YOLOX network and other mainstream detection models, the improved YOLOX model has the best detection performance. This study provides a new idea for the automation of ultrasonic testing of train wheels.

An approach to generating local oscillation (LO) microwave signals with low close-to-carrier phase noise is proposed and experimentally demonstrated based on employing cascaded optoelectronic oscillators (OEOs). In this scheme, an actively mode-locked OEO (AML-OEO) is used as the master OEO to generate a microwave comb with low close-to-carrier phase noise. Then, the generated microwave comb is injected into the slave OEO with a well-designed loop delay to form an injection-locked OEO (IL-OEO). Owing to the different transmission frequency response curves between the two OEO loops, a single tooth is selected from the injected microwave comb and is regenerated in the slave OEO cavity, while the unselected teeth are effectively suppressed. Benefited from the injection locking effect, the low close-to-carrier phase noise characteristic of the microwave comb from the AML-OEO is transferred to the regenerated LO microwave signal from the slave OEO. In such a case, an LO microwave signal with low close-to-carrier phase noise is generated by the proposed cascaded OEOs. A proof-of-concept experiment is carried out to verify the feasibility of this scheme. In the experiment, an LO microwave signal at 10 GHz is generated, where the spurious suppression ratio and the close-to-carrier phase noise are measured to be 22 dB and -85 dBc/Hz@10 Hz, respectively. Compared to the LO microwave signal directly generated by the conventional OEO, the close-to-carrier phase noise is reduced by more than 30 dB.

Tunability of optical responses is crucial to the development of optical switch and optical code. The methods of light intensity modulation of changing external voltage, temperature, or hydrogen exposure of devices limit the flexible and realtime control of modulation. Herein, we propose a polarization-modulated nanosystem consisting of Au grating, TiN film, and SiO₂ substate. The light reflection intensity is controlled by changing the polarization angles of the incident light. By adjusting the polarization state of incident light from transverse magnetic (TM) polarization state to transverse electric (TE) polarization state, the proposed nanosystem exhibits a plasmonic switch effect with reflection from 14.2% to 86.8%, and obtains a relative modulation depth is 511.3%. The reason of the light intensity modulation is the synergistic effect of the SPPs mode at the interfaces of Au/air and TiN/air excited by TM polarized light. The proposed nanosystem enriches the methods for light intensity modulation, and has potential applications in many fields including optical switch and optical code.

Due to the wide application of welding in the modern industry, effective detection of weld surface defects is an important measure to ensure the quality of components, monitor the Service life of the structure, and ensure the safety of users. However, there are wrinkles and stains on the weld surface, which makes detection difficult. Based on the dynamic detection of pulsed eddy current thermography, a multi-feature fusion algorithm of infrared features and visible information is proposed in this paper. In dynamic detection, the relative position of cracks in the field of view is constantly changing, therefore, the thermal image sequences are spatially aligned to obtain the transient thermal response curve in static mode. Feature extraction and dimensionality reduction of thermal image sequences are carried out in time domain. The processed data is fused with the visible image features, and classified in pixel-level applying the pattern recognition network. The experimental results show that the proposed algorithm can effectively suppress the noise caused by weld texture and surface stains, and obtain more clear and accurate defect information. All 21 weld surface defects can be detected, and the detection ability is greatly improved.

Fringe projection profiling (FPP) is a technique to obtain the three-dimensional shape of an object by projecting periodic fringes onto its surface and analyzing the modulated fringes.The goal of this technique is to quickly and accurately obtain the three-dimensional shape of an object with as few fringe patterns as possible. This paper combines the fringe analysis steps of fringe projection profiling and deep learning, the proposed DARUNet network (Dense and Residual U-Net) introduces Dense Block and Residual Block on the basis of U-Net. Only three modulated fringe patterns with different frequencies need to be captured as the input of the DARUNet network, the network outputs the numerator and denominator of the wrapped phase corresponding to each frequency. After some post-processing, the three-dimensional shape of the object can be obtained. Deep learning relies on high-quality datasets, so this paper compares two methods for temporal phase unwrapping: Multi-frequency (hierarchical) and Multi-wavelength (heterodyne).The Multi-frequency method, which demonstrated superior performance, was chosen to create a high-precision 3D measurement dataset. Experiments show that the proposed network has higher precision in predicting the wrapped phase than U-Net and its series networks, and predicting the numerator and denominator of wrapped phase by fringes is also the optimal route for 3D reconstruction technology based on deep learning, this method achieves a high level of precision with a phase error of less than 0.1 radians and a depth error of less than 0.3 mm. Therefore, the method employed in this paper enables high-precision 3D measurements using only three frames of fringe patterns.

Three-Dimensional Displacement Sensing has a very important demand in research fields such as nanomanufacturing, lithography, and microscopic imaging. Optical displacement sensing has received considerable attention in recent years due to the advantages of non-contact and high-precision, etc. However, traditional methods that use optical phase or polarization singularities to obtain position information are affected by the intensity of light, making the detection difficult. Here, we propose a nanoparticle on waveguide film structure that utilizes the nanoparticle as a near-field probe to achieve three-dimensional displacement sensing. The scattering light of the nanoparticle excites the resonance modes of the waveguide structure and projects the generated signal to the far field. The far-field distribution has a strong angular correlation, and by detecting the relative strength of the corresponding angle in the far-field distribution, it is possible to achieve three-dimensional displacement sensing. We have theoretically verified this idea through the finite difference time domain (FDTD) method. The three-dimensional displacement sensor implemented by this structure may be applied in nanometrology, nanofabrication, and super-resolution microscopes.

Frequency conversion in homogeneous crystals suffers from a well-known trade-off: one can only achieve high frequency-conversion efficiency for a narrow acceptance bandwidth or vice versa. Nevertheless, adiabatic frequency conversion in non-homogeneous crystals may address the trade-off dilemma, allowing for both efficient and broad-bandwidth frequency conversion. A novel adiabatic nonlinear optical frequency conversion method based on the electro-optic effect is proposed, which can be applied in a plethora of bulky nonlinear crystals. In the method, the nonlinear crystal is placed in an electric field which modulates the refractive index in order to tune the phase mismatch. When the intensity of the electric field slowly and monotonously varies in space, the phase mismatch in the crystal varies accordingly, and in this way adiabatic frequency conversion can be attained. The validity and feasibility of this new approach is demonstrated by providing a theoretical framework and experimental evidence. In the experiment, the second harmonic generation of 532 nm is conducted in KD₂PO₄. Conversion efficiency approaching 47.2% is achieved, with a corresponding temperature acceptance bandwidth of 4.56°C, which is about 4.3 times the temperature without the external electric field. The approach based on electro-optic effect is promising to extend the range of applications of adiabatic frequency conversion and, consequently, to achieve efficient and robust frequency conversion. Moreover, when phase matching is disrupted by variations in system parameters, it is convenient to adjust the voltage to recover the phase-matched state, and which can further broaden the acceptance parameter bandwidth.

Terahertz (THz) imaging technology has garnered considerable attention across a range of fields. However, its progress is constrained by the challenge of achieving high resolution. The terajet effect, utilizing dielectric structures, has emerged for super-resolution THz imaging. Nevertheless, the short terajets generated by the reported structures pose challenges for practical matching with the experimental setup. This study introduces a novel approach employing core-shell microspheres to generate long terajets with tunable characteristics. Numerical simulations reveal that precise tuning of core-shell properties leads to diverse terajets characteristics, encompassing variations in maximum intensity (53.6 V²/m² to 261 V²/m²), focal length (0.05 λ to 3.8 λ), working distance (1.15 λ to 13.6 λ), and full width at half maximum (0.37 λ to 0.91 λ). These findings highlight the tunable potential of core-shell microspheres, holding promise for enhanced terahertz zoom imaging with improved resolution and adaptability.

High-power vertical cavity surface emitting lasers (VCSELs) are widely used in optical communication, optical storage, optical interconnection, sensing, and other fields. High-power VCSELs usually adopt a high-density array layout, and temperature is one of the key factors affecting their performance. In this work, the thermal characteristics of the VCSEL array with 1273 elements have been studied. A series of photoelectric characteristics such as the working voltage, output optical power, slope efficiency, electro-optical conversion efficiency, and spectrum of the device have been analyzed through a precision temperature control system. According to the relationship between the measured wavelength shift and the dissipated power, it is calculated that the thermal resistance value of the device increases from 1.319℃/W to 1.952℃/W, and the temperature rise of the active area is extracted. It can be seen that more temperature rises in the active region at higher ambient temperature for a given injection current, with a maximum value of 105.6℃. A thermo-electric coupling model was established to simulate the thermal distribution. The equivalent array method is employed to simplify the high-density array. The simulated results agree well with the measurement. As the ambient temperature rises, the thermal crosstalk phenomenon in the VCSEL array becomes more obvious. Heat diffusion becomes more difficult, resulting in more heat accumulation inside the device. The internal loss of the device is severe and the gain-cavity mode is seriously mismatched, so the photoelectric performance decays sharply. This research provides important guidance for the optimization and application of future devices.

Aiming to optimiziong axial chromatic aberration, this paper designed and compared three different dispersion lens configurations for spectral confocal displacement sensor. The designed three-piece dispersion lens exhibited a dispersion range of 6.706 mm, a linear fitting error of 50 nm, and a diffraction limit of 739 μm. The designed four-piece dispersion lens ultilized a dispersion range of 0.992 mm, a linear fitting error of 12 nm, and a diffraction limit of 30 μm. The designed five-piece dispersion lens yielded a dispersion range of 2.174 mm, a linear fitting error of 30 nm, and a diffraction limit of 69 μm. In summary, three-piece lens offered the largest detection range and a smaller linear fitting error. On the other hand, the four-piece lens exhibited the smallest dispersion range, while the fitting error and the diffraction limit were boasted the smallest to that of the three-piece lens. In terms of convenience of assembly and machining, the three-piece lens was superior, with identical glass types that facilitated easier processing and higher cost performance. However, for a balance between resolution and dispersion range, the five-piece dispersion lens should be the better choice.

With the rapid development of global communications and exponential growth of network traffic, the flexibility and dynamism of the modulation format and the transmission rate have become important characteristics of the development of the next generation of optical networks. The optical network must be capable of dynamically transferring signals of different modulation formats and data rates to satisfy the requirements of flexible and high-capacity optical network transmission. In this work, we propose a modulation format identification method based on the mean-shift cluster algorithm to implement the reception of different modulation format signals in high-speed optical communication adaptively. The proposed MFI is a spatial cluster method based on density distribution, which can automatically extract the cluster number and density information of samples by estimating the density distribution of samples in the space. In this paper, we construct a 10 GBaud coherent optical simulation system, transmitting QPSK, 8QAM, 16QAM, 32QAM, and 64QAM, to verify the feasibility of this method. The transmission fiber length of the simulation system is set to 80 km. In the case of considering the CD dispersion parameter to 16 ps/(nm·km) and the linewidth is 100 kHz, the simulation results show that the proposed MFI method can achieve 100% identification accuracy when the OSNR values are lower than the 7% FEC limit corresponding to the lowest required OSNR values for five commonly used modulation formats (MFs). Among them, when the OSNR values of 16QAM and 32QAM signals respectively are 17 dB and 21 dB, the identification rate reaches 100%, which can effectively complete the high-precision classification of different modulation formats.

A parameter optimization method is proposed to enhance the performance of integral imaging (InI) and super multi-view (SMV) in light field three-dimensional (3D) display. The parameters of the light field display are categorized as system parameters and display parameters. By employing a multi-objective genetic algorithm, we optimize the system parameters to achieve the desired values for the display parameters. This approach takes into account the comprehensive impact of all display parameters on the imaging quality of light field 3D display. By setting different combinations of the weights in the genetic algorithm, the resolution, DOF and FOV is improved, respectively.

This paper presents a double-pass low-noise bismuth-doped fiber amplifier based on a Sagnac comb filter. The amplifier utilizes a Sagnac loop to filter out spontaneous emission light outside the signal wavelength, effectively decreasing the noise figure. Experimental results show that the amplifier achieves a minimum noise figure of only around 3.7 dB. Moreover, its gain bandwidth can cover a significant portion of the O-band. Under a forward pump power of 0.538 W, with an input signal power of -30 dBm, the amplifier can reach a gain of 29.6 dB, while the noise figure is only approximately 4 dB. Under backward pump, the gain difference for different input signal powers is larger compared to forward pump. We also studied the variation of gain with input signal power at a pump power of 0.5 W, using both forward and backward pump methods. The results indicate that the pump direction has a minor impact on the gain but significantly affects the noise figure, with the noise figure under forward pump being 1-2 dB lower than that under backward pump. Additionally, the amplifier exhibits a maximum saturation output power of approximately 9.5 dBm. In conclusion, this amplifier has great potential for application in WDM communication systems.

Time-frequency synchronization is a basic element in some fields such as deep space exploration and satellite navigation. Its accuracy and precision are closely related to the measurement results of these systems. In high signal-to-noise ratio situation, the accuracy of time-frequency synchronization is affected by the Doppler frequency shift. In this study, we propose an interpolation model that can mitigate the impact of the Doppler frequency shift, which is constructed from the prior information of the system and related to phase difference of the pseudo-random code. A coherent heterodyne ranging system is built, which is phase-modulated by pseudo-random binary code. And interpolation model is experimentally verified. The experimental results show that the ranging deviation is not more than 0.55 mm for static target. For the moving target, the ranging deviation does not exceed 0.40 mm, and the deviation of the velocity measurement is within 0.45 mm/s.

Phase sensitive optical time-domain reflectometry (Φ-OTDR) based on ultra-weak fiber Bragg grating (UWFBG) array measures the dynamic strain by extracting the phase of the reflective signals. However, the performance is challenged by the trade-off between spatial resolution and sensing distance. In this paper, we propose a wavelength division multiplexed (WDM) Φ-OTDR based on a cross-arranged dual-wavelength UWFBG array to overcome this limitation. By combining the vibration positioning results of two wavelengths, high resolution and long sensing distance can be achieved at the same time.

Transport of intensity equation (TIE) provides a powerful QPI means due to its simplicity and high efficiency. However, it is limited in dynamic measurement because it requires at least two defocus intensity images acquisition. Therefore, a simple, accurate, full-field single-shot QPI method is proposed based on TIE and wavelength multiplexing scheme. By ultizing the different phase modulation capabilities of liquid crystal spatial light modulator (LC-SLM) for different wavelengths of light, multiple intensity images of different defocus distances can be produced by a Fresnel-lens-loaded LC-SLM. In this manner, those images can be acquired by a color camera with single exposure, enabling dynamic QPI application. computational imaging.

Airborne Lidar Bathymetry measures ocean depth by transmitting 532nm wavelength lasers and recording the return energy and moment of the laser echo, and is an important means of acquiring the topography of coastal zones and shallow seas. Since underwater targets can also reflect the emitted laser, bathymetric lidar holds promise for underwater target detection. However, most of the existing echo simulation models for laser underwater transmission are for full field-of-view (FOV) and flat terrain, but there are few echo simulation models for hovering targets with sizes smaller than the FOV. Therefore, we combined the ray tracing and semi-analytical Montecarlo methods to simulate the laser echo energy of underwater targets. The model combined the speed advantage of the semi-analytical Montecarlo method with the ability to simulate echoes of underwater targets of arbitrary shapes. In order to simulate bathymetric lidar echoes under real operating conditions, the model also included simulations of the scanning mode and surface waves. The trend of the echo energy of an underwater target within the field of view with the deviation distance from the line-of-sight axis was investigated, and the results showed that even if the underwater target is deviated from the main axis, there is still an obvious target echo due to the scattering of the laser in the water, and the echo energy is weakened with the increase of the depth. The waves can make the ideal refraction direction change, which has a great impact on the quality of the scanned point cloud.

In this study, we developed a twisted optical fiber surface plasma resonance (SPR) refractive index sensor using the helical structure of a dual side-hole fiber (DSHF) to measure refractive index sensitivity. The sensor structure consists of the helical DSHF integrated into a single-mode fiber (SMF) and a multimode fiber (MMF). Our experimental findings demonstrate that the twisted SPR refractive index sensor based on the helical DSHF exhibits excellent responsiveness within the refractive index range of 1.33 to 1.38, with a sensitivity of 1998.09 nm/RIU and a high linear correlation coefficient of 0.9571. This helical DSHF design offers numerous advantages, including high sensitivity, remarkable linearity, a wide measurement range, and ease of manufacturing.

In this paper, based on the amplified spontaneous emission (ASE)-induced limited-band white noise modulation, a short-coherence laser source is developed for the wafer dynamic profilometry. All-fiber Mach-Zehnder optical path is constructed, obtaining the orthogonal-polarized light source with optical path matching for short-coherence dynamic interferometry. The 220-μm coherence length and 28 % side lobe suppression ratio (SLSR) of the modulated laser are realized in Fizeau interferometer. The dynamic profilometry of a 100-mm high-Al-doped glass wafer with 1.5-mm thickness is realized in the common-path interferometer, overcoming the interference fringe crosstalk induced by the front and rear transparent surfaces.

Low coherent pulse bound states have drawn significant interests due to their distinctive structures and dynamic behaviors. Single- or dual-wavelength interference-induced noise-like soliton molecules (NLSMs) characterized by the crossing features of a broad autocorrelation pedestal of noise-like pulses (NLPs) and symmetrically distributed autocorrelation multi-spikes of soliton molecules (SMs) are experimentally achieved in a fiber laser with a dualcavity structure, respectively. The generation of NLSM owes to the intrapulse interference within an NLP or interpulse interference between two NLPs, exhibiting its coherence varying from weak to strong. Moreover, the coherent pulse spacing within NLSMs can change from 8.42 to 44.93 ps by altering length differences between two subcavities. Our work provides a novel approach for manipulating low coherent pulse generation.

We propose a novel approach for the automated reproduction process of mode-locked pulse generation in a fiber laser, employing a statistical correlation analysis algorithm to execute rapid spectrum searching and matching. Our system incorporates a servo-based automatic control strategy to realize precise reconstruction of specific mode-locked states from white noise in accordance with desired spectral characteristics. The average reproduction time is 70 ms for a similarity, defined by the percentage error between targeted and matched spectra, of 98.96%. Consequently, our real-time reproduction algorithm offers a highly promising method for the automated manipulation of mode-locked pulse generation in laser industry.

In terahertz (THz) time-domain spectroscopy, the excitation of THz waves by fiber optic transmission of femtosecond pulsed lasers can provide great convenience for nondestructive testing of large and medium-sized aircraft. However, due to the high peak power characteristics of the femtosecond laser, the pulse spreading and distortion caused by fiber dispersion and nonlinearity can seriously affect the output laser pulse quality and the excitation of THz waves. In this paper, a three-segment femtosecond laser transmission scheme using asymmetric dual-core fiber (ADCF)-single-mode fiber (SMF)-dispersion-compensated fiber (DCF) is proposed. The simulation study results show that the strong dispersion using a 2.8-cm-long ADCF can reduce the 1 kW peak power to 8.03 W and extend the 50 fs pulse width to 3.74 ps, respectively. The spreading pulse can be restored to the peak power of 987.20 W and pulse width of 51.80 fs after the 10m-long SMF and then transmitted by the 66.9 cm-long DCF. This shows that the proposed femtosecond laser transmission scheme can achieve good pulse recompression and simultaneous recovery of pulse waveform and power, which lays the foundation for the construction of further THz time-domain spectroscopy systems using longer fibers for femtosecond laser transmission.

Ultraviolet communication, as a new type of communication, has the advantages of strong anti-interference ability, non-line-of-sight(NLOS), and all-weather operation, so it has been emphasized and become one of the research focuses in the field of wireless communication. And the light source beam angle directly determines the distance and performance of communication, but most of the current studies are limited to simulation to analyze the influence of the beam angle. In this paper, in order to verify the effect of light source beam angle on the performance of line-of-sight(LOS) and NLOS communication systems, four types of collimator lenses for controlling the light source beam angle are designed and molded, and comparative analyses of simulations and measurements are carried out. The result shows that in LOS communication, the smaller the beam angle is, the better the system performance is. In NLOS communication, the change of beam angle has less change on the path loss and almost no effect on the system performance. The conclusion are of guiding significance in promoting the practical application of ultraviolet communication.

A physical model of the Littman configuration external cavity diode laser is established based on the angular spectrum theory, and the external cavity transfer function is derived. The wavelength-dependent coupling efficiency is calculated, obtaining the external cavity filtering envelope. Based on this model, we numerically simulate the filtering envelope with different parameters. The simulation shows that the filtering bandwidth of the external cavity narrows with the decrease of the collimator focal length. The wave aberrations of the collimator lens seriously degrade the peak reflectivity and filtering bandwidth of the external cavity. The impact of the external cavity length and the beam misalignment on the filtering function is studied, providing a theoretical basis for the error analysis of the optical path design.

Multi-Frame Blind Deconvolution (MFBD) algorithm is the mainstream post-processing method for atmospheric turbulence degraded images. The restoration of a single object from multiple images requires several minutes or even tens of minutes, which severely limits MFBD’s practical application. To achieve the goal of fast restoration, this paper proposes hybrid MPI-CUDA (Message Passing Interface-Compute Unified Device Architecture) accelerated MFBD algorithm. In this hybrid programming model, MPI is responsible for assigning computing tasks, and CUDA is responsible for parallel computing. Hybrid MPI-CUDA accelerated MFBD algorithm has been tested on simulated images and achieved satisfactory results. The execution speed for restoring a single high-resolution image from multiple blurred images has been increased by over 50-fold.

In order to solve the problems of fiber nonlinear effects due to constellation expansion and the reduction of information entropy due to constellation shaping, an 8-dimensional trellis coded 16-quadrature amplitude modulation format with probabilistic-geometric joint shaping (8D-TCM-PS-GS-16QAM) in high-speed optical communications is proposed. The BER performance of 8D-TCM-PS-GS-16QAM signals with unshaped, geometrical shaping only, and probabilistic-geometrical joint shaping (H=14/13/12 bits/symbol) is simulated. At a BER of 3.8e-3, the four shaped signals are able to obtain a gain of 0.36dB, 1.52dB, 2.02dB, and 2.46dB, respectively, compared with the unshaped signal. The BER performance of low-dimensional, i.e., 2D and 4D signals is also simulated. Comparing the gains obtained for 8D-TCM-PS- GS-16QAM (H=14 bits/symbol), 4D-TCM-PS-GS-16QAM (H=6 bits/symbol), and 2D-TCM-PS-GS-16QAM (H=2 bits/symbol) with the unshaped signals in the corresponding dimensions, the gains obtained at 3.8e -3 BER, are 1.52 dB, 2.29 dB, and 4.16 dB, respectively. Constellation shaping causes all three to sacrifice the same total information entropy of 1bits/symbol, but the information entropy sacrificed by the basic 2D constellations of the 8D signal is only 50%, 25% of that of the 4D and 2D signals. Meanwhile, the shaping gain obtained by the 8D signal reaches 66.4% and 36.5% of the 4D and 2D signals, respectively. This scheme enables the whole scheme to flexibly adjust the spectral efficiency (SE). Meanwhile, it increases the degree of freedom of the signal. This scheme can realize high BER performance transmission of high SE signals. It has great potential for future construction in high-capacity and high-speed optical communications.

In contemporary film and television production, LED screens are commonly used as dynamic backgrounds, but moiré problems are often encountered. Existing studies on moiré control predominantly employ pre- or post-production removal methods, which exhibit limitations when applied to high technical specification images. To avoid moiré during the on-set shooting, cameramen often resort to techniques such as defocusing, the effect of which relies much on experience and expertise, and cannot entirely exclude the persistent occurrence of moiré phenomena in defocused scenarios. To address these issues, a more quantitative comprehension of the factors governing moiré formation is imperative. Previous explanations such as interference superposition of gratings or undersampling have proven inadequate in accurately simulating moiré on LED screens and therefore cannot effectively guide practice. We propose a convolutional imaging calculation-based approach for simulating the moiré pattern observed in screen shots. The simulated results exhibit consistent global patterns of moiré and their variation trends with shooting parameters, as compared to live results. We compare the moiré images generated through simulation methods with those obtained from live shooting experiments, while investigating the influential factors of moiré control during the live shooting. For various focusing scenarios, we present a constraint inequality for the shooting parameters, and demonstrate its efficacy in accurately predicting moiré reduction during defocused screen shooting. Furthermore, we apply this method to quantify the impact of camera roll rotation, LED screen dot pitch, opening ratio and pixel arrangement on moiré formation.

We present an equivalent circuit model for a silicon microring modulator (MRM), aiming to accurately describe its behavior in high-speed modulation. The model consists of two parts: the first part accounts for electrical parasitics arising from PN phase shifters and pads, while the second part represents the RLC circuit responsible for capturing optical dynamics of MRMs. Model parameters were derived through curve fitting, utilizing Si MRM characterization data. At data rates of 80Gb/s and 106Gb/s, simulated eye diagrams align perfectly with measured eye diagrams. The equivalent circuit model can be effectively used for electronics and photonics co-design.

In order to bring frequency combs out of well-controlled laboratory environments, a robust mode-locked fiber laser is preferable with enhanced self-starting capability, and reduced size, weight, and power (SWaP). We try to reduce cavity loss as much as possible to lower the self-starting threshold and operation power. A lower concentration doped-fiber could restrain non-radiative transitions and scattering from color centers, which are two main loss sources of active fibers. We performed comparison experiments using two fibers with different rare-earth doping concentrations for better SWaP performance. Experimental results match with our predictions. Pumped by a 980nm semiconductor external-cavity stabilized diode laser, a mode-locking self-starts at about 60mW. The net-dispersion is managed by balancing the lengths of the positively dispersive Er-doped fiber with the negatively dispersive PM1550 fiber. It is worth noting that the passive mode-locking can be maintained with pump power as low as 30mW. The laser central wavelength is 1560nm and 3db bandwidth is about 42nm, corresponding to a transform-limited pulse duration of 61.43fs assuming sech2 pulse shape. The repetition frequency is 47.41MHz with more than 90dB signal-to-noise ration at 1KHz resolution bandwidth. At the minimum pump power, the laser output is at 4.2mW average power.

Aiming at the characteristics of vortex beam and plane wave interference, as well as vortex beam self-conjugate interference, this report presents methods for microscopic displacement measurements using petal-like interferograms of vortex beam interference, which has been validated by theoretical analysis, simulations and experiments. On the basis of verifying the linear relationship between interference fringe Angle and micro-displacement through experiments, further, the information processing of petal-like interferogram is explored, and the corresponding fringe extraction method and error correction method are proposed, which provides a new detection scheme and technical approach for eddy light interference detection to be applied to nano level micro-displacement measurement.

The integrated mutual injection laser consists of a front section laser (FSL), a phase-section laser and a rear section laser (RSL). By adjusting the current of the two DFB lasers, the cavity modes of the FSL and RSL coexist in a period-one (P1) state, and the integrated laser is a dual-mode output. The beat frequency (fLO) can be obtained as the optical local oscillator (LO) frequency. When the linear frequency modulation (LFM) signal is directly modulated onto the front section laser of the integrated laser, after passing through the photodetector, the two main oscillation modes will beat with the first-order optical modulation sideband of the other mode, thereby generating the new frequency signals (f_LO±f_LFM). When the fundamental frequency signal or fLO is tuned, a double chirp signal with opposite chirp rate can be generated in different frequency ranges. In the simulation experiment demonstration, DCMWs in the frequency range of 11~17 GHz and 5~9 GHz are obtained respectively, and the corresponding time bandwidth product (TBWP) reaches 800. The full width at half maximum (FWHM) can reach 0.272 ns, and the peak sidelobe ratio (PSR) can reach 21.45 dB. The scheme is beneficial to further enrich the transmitting frequency band of radar detection signal. The principle is simple, the integration is high, the operation is convenient, and the frequency is adjustable.

Gratings, as important optical elements, are widely applied in the field of optical metrology as well as spectral purity. With the gradual decrease in the measuring wavelength to ensure high sensitivity, the scalar diffraction model has once again gained attention as a fast method for obtaining diffraction results and analyzing physical processes. This paper provides a detailed deduction of the reflected diffraction efficiency of an asymmetric trapezoid grating using the scalar diffraction theory, and demonstrates its validity and accuracy by comparing it with the vector diffraction theory. Building upon the scalar model, we further developed a rapid reconstruction model to determine the grating structure using an intelligence optimization method, namely an improved particle swarm optimization algorithm with random perturbation. The method eliminates the need for creating a large dataset for model training, while still providing a relatively accurate measurement result. It can be seen as a step towards narrowing the search range of feasible solutions, which significantly improves the efficiency of metrology.

A cost-effective 46.9 W diffraction-limited all-fiber laser at 980 nm was demonstrated with a 20/80-μm octagonal double-cladding Yb-doped fiber under direct pumping of low-cost 915 nm laser diode. The slope efficiency is about 24% and the center wavelength is 977 nm. The beam quality M² factor is measured to be 1.30 (Mx² = 1.40, My² = 1.19). The amplified spontaneous emission at 1030 nm is about 50 dB lower spectrally at the maximum output power. To understand the laser generation process and optimize the output performance, we investigated the effect of gain fiber length on the output power characteristics both experimentally and theoretically. The experimental results are consistent with the simulation.

In solving the problem of random launch of long-distance and high-precision strategic missile trains, the passive autonomous navigation mode dominated by inertial navigation (INS) shows its unique advantages, but the Inertial navigation system has the problem that the accumulated error cannot be eliminated, which cannot meet the practical application requirements, and needs to be assisted by other navigation means. As a passive and fully autonomous navigation system, geomagnetic navigation has the advantages of low cost, anti-interference, all region, small size, and no accumulated error, which can effectively compensate for the shortcomings of other current navigation systems. In this paper, we introduce high-precision laser Doppler velocimeter (LDV) and geomagnetic sensor into the integrated system, and propose a geomagnetic sensor assisted INS/LDV integrated positioning scheme. On the basis of INS/LDV integration, we design INS/LDV/geomagnetic sensor integrated navigation system and algorithm, correct the error of NS/LDV integrated navigation system, and further improve the integrated navigation positioning accuracy.

Quantum cascade lasers (QCLs) are semiconductor lasers that generate photons through intersubband transition in quantum well structures. Nowadays, QCLs can cover the mid-infrared wavelength range, making them excellent for sensing and spectroscopy. In the last decade, it is found that QCLs can directly output frequency modulated frequency combs due to the four-wave mixing process introduces a large nonlinearity into the cavity. Flat and slightly negative group velocity dispersion (GVD) are favorable for the generation of frequency combs in QCLs. Therefore, many efforts have been devoted to engineer the dispersion of the QCL cavity in recent years. In this paper, we propose the use of silicon photonic integrated circuits as a dispersion compensation scheme for QCLs. The light from the QCL is coupled to the silicon-on-sapphire (SOS) waveguide through butt-coupling. A loop mirror consisting of coupled SOS waveguides is employed to provide the optical feedback and dispersion compensation. The antisymmetric super-mode of TM₀ and TM₁ in the coupled waveguides are selected to compensate the positive GVD (~1000fs²/mm) of the QCL. This numerical study paves the way to hybrid integration of QCL frequency combs with silicon photonics integrated circuits.

Draw tower grating (DTG) with large capacity, long distance, fast response and other advantages is rapidly becoming the current mainstream fiber optic sensors, but want to write high reflectivity fiber on the draw tower fiber is particularly difficult. Therefore, it is important to further study the grating formation mechanism of fiber gratings for the rapid preparation and wide application of DTG. We will four different types of pure silicon dioxide optical fiber core fiber and G654E bend-resistant fiber for multi-pulse writing experiments. In pure SiO₂, due to the lack of oxygen conditions Si-O-Si structure in the middle of the position of the oxygen atom will produce neutral oxygen vacancies, when the capture of a positively charged hole will form a SiE' color centred, while the experimental results of two pure dioxide optical fiber and can not be inscribed out of the grating, indicating that defects in the optical fiber is not a defect in the color centred is not a necessary condition for the formation of optical fiber into the grating. In order to further investigate the role of the color centred on the refractive index modulation of optical fibers, the above fiber for high-pressure hydrogen-carrying experiments, the hydrogen-carrying fiber for the multi-pulse writing experiments, found that there is still a pure dioxide optical fiber can not be written into the grating, and the remaining four types of optical fiber emissivity have a greater increase, to verify that the color centred model of the refractive index modulation of optical fibers is not a direct contribution to the indirect.

Diffraction lens had been widely used in the field of super-resolution imaging, laser dicing, and particle trapping. Although Greek-ladder photon sieves is a kind of amplitude-only diffraction lens and suitable for EUV and soft x-ray focusing and imaging, the focal length are hard to be measured precisely by non-destruction testing due to its fine feature. Here quasi-Walsh phase retrieval is proposed to measure the focal length in one-single exposure. Compared to the random scatter plate, a quasi-Walsh phase plate can not only greatly decrease the alignment precision, but also provide the unique solution of the test wavefront. Simulation experiments show that the proposed single-shot Walsh-modulation phase retrieval can measure the focal lengths of the Greek-ladder photon sieves with high precision, which can greatly facilitate the development of multi-focal diffraction lens.

Some people utilize micro-cameras to spy upon other people or important confidential items. This kind of behavior severely affects people’s privacy securities and government’s intellectual safeties. Micro-cameras, however, are hard to be recognized by human eyes and do not spread any signals or radiations. This paper analyzes the basic principle of the cateye effect and states its advantage by applying the cat-eye effect on micro-camera detection. Furthermore, the activedetection model based on cat-eye effect is analyzed in this paper in order to explore the relationship between the detection efficiencies of micro-cameras and the incident angles of the laser beam to the micro-cameras. By applying the knowledge of geometric optics and wave optics, the specific structure of a micro-camera and spectral characteristics of reflections are analyzed. This study calculates and simulates the echo light field with different incident angles at a certain detection distance. Based on the physics model, an active detection system is set up. The experiment results prove the feasibility of utilizing the cat-eye effect to detect micro-cameras; in addition, the intensities of the diffracted light fields decrease with the increase of incident angles, and it is still effective within 10 degrees of the incident angle. The experimental results and mathematical analysis verify the reliability of the detection effect at different incident angles.

We have developed fast and accurate protocols for ion shuttling in a surface-electrode ion trap, which allows efficient splitting and merging of two ions. These protocols are based on innovative improvements in the driving potential field model, where voltage is introduced as a variable parameter. This enhancement specifically addresses the issue of increased control errors that occur with larger inter-ion distances. We have devised a general model-solving procedure that uses a parameterized model to describe the total potential energy of the two ions and ions oscillating eigenfrequency in a dynamical normal modes. By employing optimization techniques, we determine optimal voltage ramps for the dynamic potential field, enabling accurate control of physical quantities during the splitting process. In additionally, through simulating the classical dynamics of the theoretical scheme, we decouple the ion oscillations by employing discrete Fourier transform (DFT) and nonlinear fitting techniques. Two ions are separated into individual potential wells with a distance of 200 μ𝑚 within 50 μs. The ion position drift is only 0.01%. During the splitting process, the frequency fluctuation of the center-of-mass mode of the ions is less than 0.69%, and the minimum average excitation of a single ion is 0.02 phonon. Accurate and fast ion shuttling technology facilitates the development of large-scale trapped-ion quantum computing. Maintaining the ions oscillating eigenfrequency constant during the shuttling operation alleviates the problem of decoherence of quantum information.

The hardware-in-the-loop simulation is widely used in laser semi-active guidance test, the accuracy and fidelity of diffuse laser signal is the key problem for simulation credibility. Due to the limitations of the simulation method and devices, the total energy and distribution of simulating laser had some errors, the advantage and disadvantage of laser energy attenuation methods should be judged. Combining calibration, predication and experiments, a feasible method to control laser energy attenuation was proposed. By comparing the different energy distribution state between actual condition and hardware-in-the-loop simulation, the influence mechanism of laser seeker was obtained. In conclusion it was pointed out that the different between simulation system and actual system has little influence on laser guidance. The research is helpful to design and evaluation of laser guidance simulation system.

A quadrant detector (QD) is a widely used position sensor. By employing ghost imaging, the detector's four-channel output can be multiplexed to simultaneously locate and image a target. However, flaws in the detection system distort the detected laser intensity, which will increase positioning errors and degrade the reconstructed image quality. In this study, based on the spot distribution and detector characteristics, a detection model was established and analyzed. A neural network-based fitting method is proposed to directly predict the spot location and correct the total light intensity with the detector output. The network is constructed and trained with simulated data. The prediction accuracy performance is verified by numerical simulations. This scheme has the potential to improve the localization accuracy and imaging quality of quadrant detector-based detection systems, such as radar and guidance applications.

Dynamic light scattering is often used to detect small particles, such as in industry and medicine. A typical ill-posed problem needs to be solved to recover PSD by inverting ACF data , which is a difficult problem of DLS. when DLS is used for detecting small particles in transformer oil, it is difficult to accurately recover PSD using traditional algorithms. Generalized regression neural network(GRNN) has been proved to be applicable to solving ill conditioned equations in Dynamic light scattering method. However, accurate inversion relies on proper training sets closely matching measured particle size to avoid large errors. Generating numerous samples for multimodal distributions is time-consuming. This study investigates how sample setting range affects GRNN inversion accuracy during training.The experimental system was self-built, using 362.2nm and 806.9nm polystyrene mixed diluted lotion as selected samples. The training sets were centered around theoretical particle sizes, with range variations of 10nm, 30nm, 50nm, and 100nm. The GRNN was trained using these sets, and the experiment’s light intensity autocorrelation data was input into the neural networks to obtain particle size distributions and bimodal peak particle sizes. All the sample set were achieved by measuring ACF of 362.2nm and 806.9nm polystyrene suspension on a self-built DLS experiment system. These findings indicate that closer proximity between the sample range used in neural network training and the actual situation leads to more accurate inversion results, demonstrating the network’s ability to accurately invert bimodal samples. Furthermore, the accuracy improves with more realistic training set settings. In practical measurements, combining regularization methods with this approach can enhance particle size analysis accuracy.