This PDF file contains the front matter associated with SPIE Proceedings Volume 11781, including the Title Page, Copyright information, and Table of Contents.

The accurate classification of foodborne pathogenic bacteria is an important measure to solve the food safety problem in China. Compared with the traditional spectral classification method of foodborne pathogenic bacteria, Raman spectral classification has the characteristics of high flexibility, wide range and high efficiency. This paper, by using common foodborne pathogenic bacteria as the research object, we collected article 11 kinds of pathogenic bacteria of 132 spectra data. And after preprocessing the obtained data, principal component analysis (PCA) and linear discriminant analysis (LDA) were used to extract the main feature information of the spectral data. Then, based on the continuity characteristics of the spectral data, a Raman spectral classification model of recurrent neural network (RNN) was proposed. For each RNN neuron, the model always shares its parameters and has the characteristic of memory, so it has a great advantage in learning sequential information. The experimental results show that the classification accuracy of the model is as high as 96%, higher than the traditional machine learning classification methods such as decision tree and logistic regression.

A source of isolated attosecond pulses with photon energies lying in the water window soft x-ray range is currently under development at Deutsches Elektronen-Synchrotron. Such a source will be driven by the newly developed sub-cycle millijoule-level parametric waveform synthesizer. In this proceeding on theoretical study, in order to optimize the x-ray pulse energy while maintaining good pulse isolation in the soft x-ray range, a multi-objective genetic algorithm is exploited to tailor the laser electric field waveform. The resulting synthesized waveform are then employed in a macroscopic propagation study to predict x-ray pulse characteristics from a real experiment.

In this paper, we demonstrate the refractive index (RI) sensing properties of long-period fiber gratings (LPFGs) at 2 μm. The RI sensing properties of the resonant dips of LP₀₃, LP₀₄, LP₀₅, and LP₀₆ cladding modes operating at 2 μm have been studied, respectively. The sensitivity of resonant dip of LP06 mode operating at 2 μm could reach -670 nm/RIU and - 15483.9 nm/RIU in the RI region of 1.3500-1.4500 and 1.4500-1.4624, respectively, which is higher than that of the resonant dip of lower-order cladding modes. Furthermore, the RI sensitivity can be achieved higher with the longer resonance wavelength. The proposed LPFGs-based RI sensor has potential for the next generation optical fiber sensing systems.

In fringe projection profilometry, the wrapped phase extraction is an essential process for absolute phase unwrapping and even the computation of object height information. Over the past few decades, tremendous efforts have been devoted to developing various techniques for computing wrapped phase. By contrast, the phase-shifting techniques process more advantages including higher accuracy, higher spatial resolution, and lower sensitivity to variations of background intensity and surface reflectivity. At present, a variety of phase-shifting algorithms show the comprehensive mathematical deduction and their theories are very clear. Analysis from the perspective of theoretical integrity, however, the phase-shifting techniques lack the exploration of geometric algebra. For that reason, inspired by the orthogonal resolution and resultant of forces in physics, we present a geometric analysis method. Furthermore, exploiting the proposed method to explore the double three-step algorithm, four-step algorithm and extended averaging technique, we obtain three new discoveries. Simulations and experiments have been carried out to verify the performance of these new discoveries. In addition, these results also reflect the necessity of the geometric analysis method for phase-shifting techniques.

A kind of multi-field of view (multi-FOV) hyperspectral imaging system based on mid-wave infrared (MWIR) has been developed for the first time, to the best of our knowledge. The hyperspectral imaging system is based on two focus length which can be used in different situation. According to the theory of zoom optics and the design method of infrared optics, the front telescope zoom system is calculated and designed, which is coupled with the acousto-optic tunable filter (AOTF) and the focus system to realize the infrared zoom optical system. By developing and optimizing the focus system and the MWIR detector, the +1-order diffracted light and 0-order light of AOTF can be clearly imaged on image plane. So that it can output the MWIR thermogram signal and spectrum signal at the same time. The experimental results show that the system can clearly image the target with 8km away. And the IFOV is up to 0.066mrad. The results pave the way to a novel spectrum detect technology based on infrared zoom optical system.

For the problem of dense distribution of steel structures and low efficiency of interactive point clouds extraction, an automatic segmentation algorithm of dense steel structure point clouds is proposed in the paper. Firstly, point clouds are divided into several sub blocks by Octree, meanwhile, its spatial topological neighborhood is established in the process. According to the structural characteristics of angle steel components, the Random Sample Consensus algorithm based on additional normal vector constraints is implemented to search large area plane in the sub block, and then, Euclidean distance clustering and area growth algorithm with additional smooth constraints are put forward to segment the secondary data until steel structure point clouds is clearly segmented. The validity and accuracy of the algorithm are verified by real transmission tower point clouds. The experimental results show that the automatic segmentation algorithm proposed in the paper can segment the steel structure point clouds quickly and accurately, and has high application value in future.

China’s LAMOST telescope is the most powerful spectroscopic measurement telescope for studying large field of view and large sample astronomy. It combines the world’s leading splicing mirror technology with thin mirror technology for the first time, breaking through the inability of previous astronomical instruments to combine large clear apertures and wide The bottleneck of the field of view. In order to more accurately detect the movement between the sub-mirrors of large-aperture telescopes, it is necessary to install a precise sensor at the edge of the sub-mirror to detect the movement between the sub-mirrors, and then adjust the mirror displacement in time through the force actuator under the mirror to obtain more Good image quality. Due to the particularity of the mirror surface, there are strict requirements on the displacement measurement accuracy of the sensor. Its research focuses on the acquisition and filtering of sensor displacement signals. In order to extract useful digital signals from strong noises and improve the signal-to-noise ratio (SNR) of the digital signals output by the detection system, this paper proposes a dual-channel digital filtering algorithm combining improved four-entry wavelet and adaptive filtering. By improving the four-entry wavelet algorithm, the algorithm improves the reconstruction capability and linearity while taking into account the multi-resolution characteristics of the traditional wavelet transform algorithm, and ensures the continuity of the wavelet coefficients at the threshold; and the second channel collects the high The frequency characteristic noise signal is processed again through adaptive filtering, and finally a sensor displacement signal with a higher signal-to-noise ratio (SNR) is obtained. After the front-end algorithm development is completed, the displacement signal acquisition and processing system is realized through the ZYNQ-7000 development platform, including AD conversion, digital filtering, signal transmission and LCD screen display, etc., and the Gui interface program is written using Matlab to convert the displacement signal Real-time display and save records on the PC side. The entire experiment of the displacement sensor was carried out at the Nanjing Institute of Astronomical Optics Technology, Chinese Academy of Sciences. The results show that the digital signal-to-noise ratio (SNR) processed by the algorithm is 20.7% higher than that of the traditional wavelet algorithm. The root mean square error (RMSE) of the fitted displacement curve is reduced by 19.8% on average, and the running time was reduced by 50%. It shows that the algorithm is accurate and fast, and its entire signal processing system has important application significance for the research of displacement sensors between splicing mirrors of large astronomical telescopes.

Infrared images and visible images have different imaging principles and contain different information. The fusion of infrared and visible images can synthesize the information of both, and at the same time, the complete edge structure of infrared images can guarantee the acquisition of image information under harsh and complex environments. Therefore, this paper proposes an infrared and visible image fusion method based on deep learning. Visible and infrared image pairs are divided into high-frequency and low-frequency parts in this paper. The weighted average strategy is directly used to add the low-frequency parts of the fused image. This method Uses the ResNet network to visible and infrared images of the high frequency parts of image feature extraction. FISHER discriminant method was used to screen the extracted features, and ZCA whitening was performed on the selected features to further remove the redundant information in the features. The initial weight graph was obtained by L1 generalization of the whitening features, and the final weight graph was obtained by softmax method. The high-frequency parts of infrared image and visible light image were added according to the weights to get the fused image high-frequency part, and the high and low frequency parts of the fused image were added to get the final fused image. The experimental results were compared with other methods in terms of subjective feeling and objective indicators respectively. The experimental results showed that the proposed method was more natural in fusion effect and had advantages in objective indicators.

At present, there are many kinds of composite damage self-repair methods, including non-intrinsic self-repair methods such as thermoplastic materials, microcapsules, hollow fibers, blood vessels, nanofibers and carbon nanotubes. However, none of these self-repairing methods can realize the occurrence of perceptual damage. Therefore, this paper proposes a bionic fiber, which has the functions of sensing and repairing damage simultaneously. In the process of developing bionic fiber, we choose quartz glass as the cladding material of bionic fiber, the light curing agent as the fiber core, and the plastic fiber with matching diameters as the light window to close the two ends of bionic fiber. We carried out experimental research on the fiber. Firstly, the micro-load for bionic fiber is carried out to study its micro-bending characteristics. And, the bionic fiber is damaged (micro-crack) by adding load, and the self-repair efficiency of the biomimetic fiber is studied by comparing the output optical power of the biomimetic fiber before and after the damage. Experimental results show that the bionic fiber has certain sensing and self-repairing functions, and its repair efficiency is about 40%, and the repair rate is fast. In order to make up for the large loss of bionic fiber, short bionic optical fiber can be used as the repair element in practical application, and the plastic optical fiber can be used to close the Windows at both ends and the bionic optical fiber part to form the sensing element. Therefore, the proposal of bionic fiber in this paper provides a new way and method for the application of composite material health monitoring and damage self-repair, and also provides an experimental basis for the application research of bionic fiber in intelligent composite material structure.

Since the birth of convolutional neural networks, the application of deep learning technology in image processing has been booming, and deep learning super-resolution technology is one of the most concerned fields. In the traditional deep learning super-resolution process, the conversion of high-resolution images to low-resolution images is usually obtained by down sampling, but when the actual image degradation does not conform to this process, the effect of the model is usually greatly reduced. Currently, single-frame input is mainly used for image super-resolution, but this operation usually leads to undesirable results in large-scale reconstruction. This article is derived from the SRMD network (a single convolutional super-resolution network with multiple degradations). On this basis, the key factors of image degradation (blur kernel and noise level) are added to the input of the model, and the measurement matrix commonly used in compressed sensing is used to generate multi-frame images. We invented the MFSR network (Multi-Frames Input Super-Resolution Network with Multiple Degradations), and achieved excellent results on the target data set.

High-accuracy optical time delay measurement is essential to optical beamforming networks, multi-antenna GNSS-overfiber systems, and clock synchronization networks. To meet the demand of high-performance measurement, a time delay measurement system via microwave phase shift analysis is proposed, in which a modulator bias controller (MBC) is employed to stabilize the bias point of Mach-Zehnder modulator. However, because the MBC is easy to lose lock in long-term use, the stability of the measurement system is limited. To overcome the above problem, we propose an enhanced measurement system, in which the intensity modulation is achieved using a phase modulator and an optical Hilbert transformer. To verify the performance of the proposed system, a proof-of-concept experiment is carried out. The measurement results show that an accuracy of ±0.05 ps is obtained.

We propose a method for auto-optimized compensation of pixel alignment and overall curvature in digital optical phase conjugation system named AOC-DOPC system. The theory of the AOC-DOPC system is described, and the optimized compensation capability of AOC-DOPC system is verified experimentally in the situation of system instability, overall curvature and pixel match misalignment. With the proposed system, the compensation effect is improved, the size and shape of the focus are more similar to the target pattern. Compared with the DOPC, the PIB curve showed a decrease from 0.162 to 0.007 of area ratio of 50% energy with AOC-DOPC compensation, which is about 16 times relative to the DOPC compensation. Besides, the correlation coefficient (R) increases from 0.0465 to 0.7743, which shows 3.4 times of improvement of compensation effect.

Indium tin oxide is a widely used transparent conductive oxide material. It has many excellent characteristics, such as low loss in the near-infrared region, the band gap can be adjusted by doping and other methods. ITO has recently been shown to be a good substitute for metal layer, it has obvious advantages in improve the performance of optoelectronic devices and reduce the difficulty of preparation, and it makes it possible to expand the application range of optoelectronic devices based on the multilayer film system from the visible light region to the near-infrared region. Although a large number of literatures have reported the properties of ITO films, there are few studies on ITO as a substitute for the metal layer in the multilayer film system and regulating its dielectric constant properties. In this paper, ITO films were prepared by ion beam sputtering deposition at relatively low temperature, and the dielectric constant of ITO films was regulated by change the process conditions and annealing treatment. Through experiments, we realized the regulation of near-zero point in the range of 1380nm to 2420nm, and demonstrated the change rule of the dielectric constant. Compared with metal films, optical metamaterials and devices based on ITO films can not only expand their application range from the previously visible light region to the near-infrared region, but also have wider and adjustable frequency coverage

Fluorescence lifetime imaging (FLI) plays an important role in detection of different fluorescence substances. However, when background light is strong and image noise is high, FLI is hard to discriminate substances with approximate fluorescence lifetime. An enhanced time-resolved fluorescence imaging method is proposed. In the method, a dual-gated intensity-correlation enhancement algorithm is developed. Compared with traditional rapid fluorescence lifetime determination imaging method, the method focuses on improve image contrast and can effectively remove background noise. It utilizes two fluorescence intensity images at different delay times, and adaptively chooses the filter threshold and the up threshold to remove noise and enhance contrast. The thresholds are determined by the distribution of image variance. In proof experiments, three brands of highlighters with the same color have close fluorescence lifetime, and the proposed method shows their fine fluorescence difference. The simulation and experimental results prove that the method can improve the ability of time-resolved fluorescence imaging.

In recent years, the moiré imaging device has become one of the hot topics in the field of micro optics due to its strikingly visual three-dimensional (3D) effect which can be easily recognized by naked eye. Traditionally, the moiré imaging film is composed of the superposition of a microlens array（MLA）and a micro pattern array (MPA）with high alignment accuracy. By the combination of the nanoimprinting and nanoprinting techniques, we fabricated a moiré imaging film on a large-format substrate characterized by fluorescent enhancement effect under ultraviolet light illumination. By using a novel virtual mask technique, the MPA can contain more information than traditional one. It is worthy to note that the nanostructure is introduced to the MPA to promote the light efficiency of the fluorescent material. A synthetically magnified moiré image with 3D effect is demonstrated. The moiré imaging film has widely potential applications in 3D imaging, optical anti-counterfeiting, packaging, etc.

Generally, phase-sensitive optical time-domain reflectometer (φ-OTDR) adopts a single-channel sensing structure, which makes it vulnerable to random interferences and increases the probability of vibration misjudgment in practical applications. In this paper, a dual-channel φ-OTDR based on a two-mode fiber (LP₀₁ mode and LP₁₁ mode) is constructed, and a simple demodulation algorithm is designed accordingly to locate pencil-break vibrations. The purpose of using dual-channel scheme is that the probability of false detection, simultaneously happened in double channels at the same position and at the same time, would be greatly reduced. In signal processing, both the conventional amplitude differential accumulation algorithm (DAA) and the standard variance algorithm (SVA) are employed to process the Rayleigh scattering traces of LP₀₁ and LP₁₁ channels to detect the pencil-break. The results show that the DAA is highly dependent on the parameters of the algorithm and not suitable to be directly used in practical. Due to the strong randomness of Rayleigh scattering, it is found that the pencil break cannot be detected just by the SVA. Thus, a simple method of producing two decision signals is proposed for vibration detection by combining the DAA and SVA, in which the DAA signals of one channel are crossmultiplied with the SVA signals in another channel. The results show that this method shows reliable performance of locating the pencil-break.

A novel and compact pressure sensor for marine application based on optical microfiber coupler interferometer(OMCI) is proposed theoretically. We theoretically analyzed the characteristics of OMCI's dual sensing unit, The highest pressure sensitivity of the waist sensing unit is 654pm/Mpa, and it increases with longer wavelength. The pressure sensitivity of the interference arm sensing unit is 7pm/Mpa, the sensitivity increases with the length of the embedded elastomer. Its excellent performance can provide strong theoretical guidance for the practical application of optical ocean monitoring equipment

A novel method to perform high-resolution and wideband optical vector analysis (OVA) by using fixed low-frequency detection is proposed and demonstrated. In the proposed OVA, an optical superheterodyne structure is employed to down-convert the frequency-sweeping probe signal into a fixed low-frequency photocurrent. An electrical low-speed and high-sensitivity receiver is used to extract the complex amplitude of the photocurrent accurately, which can improve the sensitivity and dynamic range of the measurement system. Besides, by using the asymmetrical double-sideband modulation (AODSB), the measurable frequency range will be expanded to twice the bandwidth of the electro-optic modulator and microwave synthesizer. Moreover, the high-speed photodetector and wideband phase-magnitude detector are omitted, which can greatly reduce the hardware cost. In an experiment, the electrical receiver works at 199 MHz and 201 MHz, respectively. The measurement range is 80 GHz, and the resolution is 200 kHz.

Vortex retarder is a simple and efficient method to generate vortex beams, and the detection of its modulation characteristics is of great significance for the preparation and application of vortex retarder. A quantitative measurement method for the two-dimensional modulation characteristics of vortex retarder based on PIE is presented. By using circularly polarized incident light, the modulation parameters of the vortex retarder are loaded into the beam phase. We report on the experimental demonstration that the high-precision reconstruction results can be achieved by applying the PIE complex amplitude measurements respectively before and after placing the vortex retarder. Based on the measurement result, the actual modulation effect of the measured vortex retarder to incident vector beam is obtained by the matrix operation and diffraction propagation. This method provides a simple and anti-interference means for quantitative detection of wave plates, liquid crystals and vortex beams.

Photoacoustic imaging is a new imaging technology in recent years, which combines the advantages of high resolution and rich contrast of optical imaging with the advantages of high penetration depth of acoustic imaging. Photoacoustic imaging has been widely used in biomedical fields, such as brain imaging, tumor detection and so on. The signal-to-noise ratio (SNR) of image signals in photoacoustic imaging is generally low due to the limitation of laser pulse energy, electromagnetic interference in the external environment and system noise. In order to solve the problem of low SNR of photoacoustic images, we use feedforward denoising convolutional neural network to further process the obtained images, so as to obtain higher SNR images and improve image quality. We use Python language to manage the referenced Python external library through Anaconda, and build a feedforward noise-reducing convolutional neural network on Pycharm platform. We first processed and segmated a training set containing 400 images, and then used it for network training. Finally, we tested it with a series of cerebrovascular photoacoustic microscopy images. The results show that the peak signal-to-noise ratio (PSNR) of the image increases significantly before and after denoising. The experimental results verify that the feed-forward noise reduction convolutional neural network can effectively improve the quality of photoacoustic microscopic images, which provides a good foundation for the subsequent biomedical research.

Fourier Ptychographic Microscopy (FPM) is a super-resolution microscopy technology, in which a set of low-resolution images containing different frequency components of the sample can be obtained by changing the angle of the light source in this technology, and then the iterative algorithm is used to reconstruct high-resolution intensity and phase information. The reconstruction usually takes a long time and is not suitable for real-time FPM imaging. It has been recognized recently that the potential fast image reconstruction algorithm is the use of deep learning algorithms. We designed a conditional generative adversarial network (cGAN) which has multi-branch input and multi-branch output which can expand the frequency spectrum of the reconstructed image very well. Based on the convolutional neural network (CNN), the brightfield and darkfield images obtained by FPM imaging can be regarded as different image features obtained by different convolutional kernel, and the skip connection of U-net can effectively utilize this information. The brightfield and darkfield images in FPM imaging are input to different branches, which can avoid missing the darkfield signal information. Importantly, the neural network we designed will continue to perform simulation process of FPM imaging from the recovered high-resolution intensity and phase to obtain low-resolution images and make them correspond one-to-one with the input low-resolution images. These corresponded images will enter loss function, making it easier for the neural network to learn relation between the low-resolution images and the high-resolution images. We validated the deep learning algorithm through simulated experimental research on biological cell imaging.

In a typical multi-kW industrial fiber laser, the influence of the main amplifier to master oscillator power ratio on laser performance has been fully demonstrated. An optimized output power ratio is obtained to be ~5, which can provide the maximum main amplifier slope efficiency of ~78.2% at multi-kW laser output. In this case, the laser setup was kept at ∼2.6kW for 1h and the output power presented a relatively small power degradation of 0.36%. It was found the injected seed power has no remarkable effect on the optimal slope efficiency for industry fiber laser. The present results indicated that a suitable power ratio between the main amplifier and the oscillator is of great importance for the power scaling up and high stability of industry fiber laser.

As an emerging nondestructive imaging technology recently, Photoacoustic imaging (PAI), which is based on Photoacoustic effect, combines the advantages: the high resolution and contrast of optical imaging and the high penetration depth of acoustic imaging. Thereinto, as a branch of Photoacoustic imaging, Photoacoustic microimaging inherited the advantages of Photoacoustic imaging. The unique focusing mode of Photoacoustic microimaging can meet the requirements of higher resolution in biological imaging, thus, it gained extensive applications in medical science field. However, on account of using high numerical aperture objective lens strongly focus on Gaussian beam, traditional Photoacoustic microimaging system has shallow depth of imaging field, and its transverse resolution and signal-to-noise ratio deteriorate rapidly outside the focal point, limiting the velocity of large volume imaging. Owing to solve these problems, in this paper, we build a simulation platform for Airy beam photoacoustic microscopy based on K-Wave simulation toolbox. This platform uses Airy beam to inspire initial Photoacoustic signal in large volume and K-Wave simulation toolbox to simulate the propagation, recording and reconstruction process of Photoacoustic signal. As Nondiffraction beam, Airy beam features the capacity of large depth of field, thus, its application could reach the requirement of large depth of field imaging of Photoacoustic microscopy system. Measuring the performances of the constructed Photoacoustic microscopy system, we constructed three-dimensional imaging of the blood vessel. By simulating A-Scan, B-Scan and C-Scan, we measured the performances of this system, such as axial resolution, transverse resolution and depth of field. Meanwhile, the three-dimensional imaging of the vertically tilted fiber also verified the three-dimensional imaging capability of the Airy beam photoacoustic microscopy simulation platform. The establishment of the simulation platform has a significance for the theoretical research of photoacoustic microscopy and its application in biomedicine.

Human female mammary gland is by skin, fibrous tissue, mammary gland and adipose composition, breast cancer is the malignant tumor that occurs in mammary gland epithelial tissue. Mammary gland is not an important organ to maintain human life activities. Breast cancer in situ is not fatal. However, due to the loss of the characteristics of normal cells, the cells are loosely connected and easy to fall off. Once cancer cells are shed, free cancer cells can spread throughout the body with blood or lymph, forming metastases and endangering life. At present, breast cancer has become a common tumor threatening women's physical and mental health. Therefore, studying the interaction of laser with breast tissue and breast tumor has important theoretical and practical significance for the treatment of breast cancer. For this reason, this study developed a two-dimensional numerical simulation model based on finite element using COMSOL Multiphysics, a commercial finite element simulation software, which studied the transmission and heat transfer of light in breast cancer patients. In this study, the model consists of four parts: 1) Water layer; 2) Breast; 3) Breast tumor; 4) short pulse laser source (wavelength: 840nm). The laser point source is located in the middle of the water layer above the breast tissue to irradiate the breast and the tumor. The propagation of light in breast and tumor was simulated by solving the diffusion equation. The temperature changes of breast tissue and breast tumor were obtained by solving the biological heat transfer equation. This study is helpful to understand the transmission of light in human breast and breast tumor as well as the interaction between the two, and has certain theoretical guiding significance for the research and treatment of breast cancer.

We proposed a single-shot diagnostic for spatiotemporal laser-plasma evolution by the multi-dimensional encoding (MuDE) holography. It can achieves high and adjustable temporal resolution measurement of three-dimensional plasma distribution without delay scanning. Experimentally, we verified the feasibility of this technique, and the retrieved results of laser-plasma evolution agreed well with the direct shadow measurement. This technique is expected to provide a helpful tool for the complex spatiotemporal evolution of plasma in ICF and high energy density physics.

We developed and verified a metrology and calibration equipment based on LabVIEW and USB-bus technology for measuring key parameters of medical laser therapy apparatus. In this paper, aiming at Q-switched Nd:YAG pulsed laser therapy apparatus whose safety and reliability issues are prominent, according to measurement requirements of key parameters during treatment, we designed a portable, high-precision, user-friendly and all-in-one measuring equipment. The designed equipment can carry out the measurement of pulsed laser key parameters including wavelength, pulse width, repetition frequency, pulsed energy or power, spot size of treatment area and beam divergence angle. For aiming beam, which is continuous wave laser, wavelength and power can be measured. In addition, the quantity values of the measuring equipment we designed were traceable to national standards of measurement effectively, which includes three items: measuring range of pulse width is 1 ns~100 ns and maximum permissible error (MPE) does not exceed ±10 %; measuring range of pulsed energy is 1 mJ~2 J, class of accuracy is up to 5, surface uniformity better than ±3 % and zero drift better than ±2 %; measuring range of treatment-area spot size is 2 mm~8 mm and MPE does not exceed ±10 %.

A refractive index sensor is a device that can convert small changes of the refractive index into an optical signal. The refractive index sensor could detect the small changes of refractive index and continuously monitor its dynamic changing process. Thus, it shows great values in detecting changes of the biochemical solutions without labeling. However, ascribed to the ohmic loss, the traditional refractive index sensor based on the noble metal usually possess low sensitivity and the figure of the merit (FOM). In this paper, an all-dielectric asymmetrical double split ring refractive index sensor with high-sensitivity and FOM is designed and numerically characterized. Here, the double split ring metamaterial structure is acted as wireless passive sensing. We used the finite element method to simulate the interaction between the incident light and the metasurface. The results show that a sharp magnetic resonance peaks could be launched caused by the all-dielectric asymmetrical double split ring. And it could greatly enhance the sensitivity and the FOM contrast to the traditional one. The results show that the resonance wavelength of the sensor is between 8270 nm - 8340 nm in the mid-infrared band. And the sensitivity and FOM of the sensor can reach 662nm/RIU and 262, respectively.

Wavefront sensor has been widely used for various research fields. Among these wavefront measuring techniques, Shack-Hartmann wavefront sensor has the merit of simple structure, real-time detection and wide waveband. Traditional Shack-Hartmann wavefront sensor is usually based on geometrical optics, which builds a micro-lens array in front of a CMOS sensor. Here amplitude-only photon-sieve array was proposed to replace the micro-lens array to reduce the cost and simultaneously to improve the measurement accuracy by super-resolution focusing of test wavefront. A simulation experiment was carried out through software GLAD and another optical experiment was implemented by Liquid crystal spatial light modulators (LC-SLM) to verify the effectiveness. As a kind of amplitude-only diffractive lens, largeaperture photon-sieve array can be easily fabricated by lithography, which has great potential to be applied for measurement of large-scale laser beam and optical element.

Based on the V-groove planing-ruling process, the Deform-3D finite element software was used to simulate the stress distribution and material flow characteristics during the planing, the residual stress of the grooved surface was analyzed using the point tracking function, and the change law of the amount of rebound was assessed. Subsequently, based on the basis of planning, the residual stress and rebound deformation change trend after completion of secondary ruling finishing was analyzed, and it was concluded that the secondary ruling finishing could effectively eliminate the rebound tendency of the V-groove, despite the notch quality being poor. It provides a new machining method for improving the quality of v-groove in industrial field.

The exciting properties of submicrometre sphere particles have been employed in many fields, such as the selective intervention characteristics and the size effect was widely used in the fields of biomedicine and sensing. However, the main synthesized methods at present were chemical or mechanical types, and several drawbacks existed. Recently, single pulsed laser irradiation in liquid has been confirmed as an innovative approach for fabrication of the submicrometre sphere particles due to the different optical absorption of precursor materials in a liquid phase, and many sphere particles for metal or alloy materials could be successfully synthesized. However, most of the semiconductor materials with low-optical absorption were disabled in this way, due to the laser energy under a proper wavelength was forbidden by the intrinsic wide bandgap of the semiconductor. Herein, based on the property of optical absorption, a double laser system was constructed to heat and assist fabrication by resonating wavelength matching. In the experiment section, the wide bandgap nanomaterials TiO₂ was employed as the precursor and irradiated at the proper wavelength that originated from the optical absorption spectrum (532 nm for Nd: YAG laser and 324 nm for OPO laser, respectively). The results indicated that the submicrometre sphere particles could be well synthesized, and the morphology, optical absorption property was obtained improvement than that way of a single pulse.

Sulfide (MoS₂) spheres were fabricated by selective laser irradiation in liquid medium, which can be applied not only in preparation of colloidal spheres, but also in synthesis of micro- and submicromaterials. The phase and size of the resulted MoS₂ spheres were found to be easily controlled by modulating input laser fluence. The influence of experimental parameters on colloidal spheres formation, including laser irradiation time, has been investigated systematically. Size-increasing and -reducing phenomenon can be observed by field-emission scanning emission microscope (FESEM), in which the average sizes of the obtained particles gradually increase with increasing laser irradiation time or fluence. Furthermore, the corresponding photocatalytic degradation rate of laser irradiated particles (61%) shows an obvious increasing when compares with the raw materials without laser processing (22%), which may provide a fast preparation way for the potential application in photocatalytic area.

Three different novel dry-etching methods have been employed to fabricate nanophotonic devices upon a thin-film lithium niobate on insulator material platform. Different dry-etching processes and their advantages, drawbacks and applicable scenarios are systematically studied. Ultra-smooth etching surface with roughness of 0.46 nm (Rq), low-loss ridge waveguides with extracted propagation loss of 1.42 dB/cm, and microring resonators with high optical quality factors up to 1.4×10⁵ are demonstrated using the optimized low-loss etching recipe. The low-loss etching technique lays a foundation for monolithic integration of passive optical components with quantum dots, on-chip broadband electro- optic modulators and wafer-scale lithium niobate integrated photonic circuits.

The staggered imaging camera is an important kind of remote sensing satellite camera. The staggered imaging technology can improve the spatial resolution of the camera without changing the focal length and pixel size of the optical system. However, the image resolution directly obtained by the staggered imaging camera is not enough. The existing traditional super-resolution methods have certain interpretability; the performance of deep learning super-resolution is related to the quality and quantity of training data set. There is no suitable data set for the remote sensing image generated by the staggered imaging system. So the frequency domain super-resolution technology is proposed for the image of the staggered imaging system. Low resolution remote sensing image can be regarded as the result of effective shift and sum of high-resolution image in time domain. There is a certain phase difference between low-resolution remote sensing image and high-resolution image in frequency domain. The time-shift property of two-dimensional image Fourier transform is used to find the difference between low-resolution image and high-resolution real image in frequency domain. The super resolution image is obtained by compensation coefficient. The frequency domain super-resolution algorithm is sensitive to noise. In order to suppress the noise interference, a special frequency domain filter is designed to filter the noise. It is verified by SPOT5 data that the frequency domain super-resolution can completely recover the noiseless image. Under the condition of image noise, the peak signal-to-noise ratio and the structure similarity can reach 35.754dB and 0.97 in 1.001 seconds.

In this work, a five-band metamaterial absorber (MMA) for temperature sensing application in terahertz region is analyzed. The MMA is composed of three layers. The bottom layer is the metallic film, the middle dielectric layer is the indium antimonide (InSb) and the top layer is the metallic pattern, in which five resonance peaks are generated. With utilizing the dielectric thermo sensitive property of InSb, the resonant absorption is tunable by varying temperature. The electric current on the MMA is investigated to better understand the physical mechanism of the resonances, revealing the resonances attributed to the high-order magnetic resonances. The multi-band absorber is insensitive to the polarization angle, and be with ultrathin thickness of structure. This design of the MMA provides a new approach for electromagnetic stealth, sensing and imaging.

When an optically rough surface is illuminated by the coherent light, we can only capture speckle pattern due to random constructive and destructive interference between light waves scattered from elementary areas of the rough surface. Here we compare two different correlography-based speckle imaging models, the results demonstrate that there is no obvious difference in imaging capabilities between two models. The spatial light propagation processes are both assumed to be far-filed Fraunhofer diffraction in two models. In order to verify the far-field distance, we capture speckle patterns in different imaging distance (range from 5cm to 100cm). We found that the far-field diffraction is always applicable in our experiments if the speckle size satisfies the Nyquist criterion, and we analyzed the relationship between speckle contrast and imaging distance, the curve of the relationship between reconstructed image size and imaging distance is fitted, the physical interpretation of the function parameters is given.

Interference wavefront detection technology has been widely used due to its non-contact, high sensitivity and high precision. Among many wavefront detection techniques, radial shearing interferometry is one of the most effective techniques because it does not need a standard reference beam, and it is easy to be designed as a common optical path without information loss and little affected by system error. However, the current radial shear interference technology still has the disadvantages that the optical path structure is not simple enough and cannot be applied to large-aperture optical systems. Focusing on the main problems of shear interference technology, we propose a radial shear interference technology based on a pair of photon sieves. A system consisting of two photon sieves can achieve radial shear interference, which greatly simplifies the optical setup and improves the stability of the optical system. In addition, the photon sieve has low manufacturing difficulty, flexible design, low cost and can meet the detection requirements of different optical systems. Therefore, the application of photon sieve in radial shear interference technology has great research significance.

The attitude determination accuracy of the star tracker is affected by many factors, among them, the centroiding accuracy of the imaging star point is one of the key factors. In this paper, a high-accuracy centroid estimation algorithm for the star tracker based on micro-pace matching and filtering is proposed. The star points are considered to be discretized sampling of the effective point spread function, in order to restore the it, it is needed to establish reference frames by micro-pace movement. Then, reference frames are interpolated, and accurate reconstruction of the star point energy distribution is obtained. In addition, Point Spread Function(PSF) correlation method is adopted to match a new star point and the reference frame to obtain the centroid displacement. Furthermore, the centroid of the new star point can be calculated. At the same time, the centroid estimation is processed by real-time Extended Kalman filter, which to some extent reduces the influence of noise, and furthermore improves the star point centroid estimation accuracy. The experiment results demonstrate that the proposed approach effectively eliminate the S-curve error of traditional centroid algorithm. The star point estimation accuracy of the proposed approach is approximate 0.0086 pixel, which is a reliable and high-accuracy result for star tracker.

The evolution properties of the normalized intensity distribution, the spectral degree of coherence (SDOC), and the spectral degree of polarization (SDOP) of a radially polarized Laguerre-Gaussian correlated Schell-model (LGCSM) beam propagating in turbulent atmosphere has been studied in detail. Based on the extended Huygens-Fresnel integral and the unified theory of coherence and polarization, analytical formulas for the elements of the cross-spectral density (CSD) matrix of a radially polarized LGCSM beam in turbulent atmosphere are derived. Numerical results show that the normalized intensity distributions of the radially polarized LGCSM beams gradually evolve from a doughnut shape into a solid spot and become a Gaussian beam profile eventually due to the anisotropic effect of atmospheric turbulence on propagation. Furthermore, the influences of the spatial coherence length, the structure constant of the refractive-index fluctuations of the turbulence, the power index, the inner scale of the turbulence and the outer scale of the turbulence on the propagation properties of the normalized intensity distributions, the SDOC, and the SDOP of the radially polarized LGCSM beams are discussed in detail.

In this work, for the first time, the chain-like ethylammonium (EA) [(C₂H₅)NH₃]⁺ caiton as an alternative cation was introduced into FAPbBr₃ cubic crystals to form the mixed-cation FA_xEA_(1-x)PbBr₃ perovskite nanowires (NWs). The results indicate that the incorporation of chain-like EA cation contributes to the inertial growth of nanowires along c axis. Replacing FA with EA can realize bandgap tuning and morphology transformation between cubic shape and nanowires. Similarly, suitable chain-like EA cation doping in MAPbBr₃ can also result in the growth of nanorods. The tuned band gap of perovskite is attributed to the variation of Pb-Br-Pb angles induced by the insertion of larger EA cation.

In the accuracy measurement of phase from interferometers with adjustable fringe contrast, it needs to estimate the contrast of experimental patterns so as to obtain the interference patterns with the maximum contrast. We develop the Fourier-polar transform and combine the directional projection to estimate the global contrast of carrier fringe pattern. The technique is especially used for low-quality fringe pattern such as low contrast and low signal to noise ratio (SNR) that often appear in the interferometric experiment. An illustrative experiment based on the radial shearing interferometer is given. Results generated from this technique are compared with the derived values from theoretical model, and exemplary agreement between both is demonstrated.

In the 3D phase measurement with large view field, when the number of fringes is not too many, the period broadening problem of projection fringes will seriously affect the accuracy of measurement. In this paper, an accurate and convenient 3D shape measurement method based on phase shifting fringe projection is prop osed. Firstly, in the fringe projection measurement system based on the triangulation principle, the fringe position coordinates are taken as the input and output parameters of the system, and the linear mathematical model of fringe period correction is de rived. Secondly, the model parameters are obtained by simple calibration process. Through using the idea of reverse fringe projection, the new fringe to be projected is calculated from the correction model, and then periodic four-step phase shifting projection fringes can be produced. Finally, a four-step phase shifting method is used to restore the 3D shape of object. The experiments of fringe period correction and 3D profile measurement show that the proposed method can easily generate the phase-shifting projection fringes with equal period distribution and hence improve the measurement accuracy of phase-shifting method.

It is a hybrid design spectrometer with MWIR zooming and spectral imaging. The system realizes the searching in large field of view and recognition in small field of view which can resolve the difficulty that the target and background of spectrometer are not easy to distinguish in a single field of view. It also decreases the difficulty of spectral analysis and data dimension reduction. The collimating light beam modulated by AOTF (acousto-optic tunable filter) provides a basis for the subsequent spectral analysis. The optical system realizes three times zoom from 160mm to 480mm. The simulation achieves the effect imaging result. Experiments show that the system has both imaging and spectral recognition capabilities.

Achromatic systems are the most common type of optical systems. At present, the selection of the designed wavelength band of the achromatic systems is mainly determined by the reception range of the human eyes or the detectors, or by previous experience. In this paper, a more accurate method to determine the designed waveband range of achromatic system is proposed. Firstly, the characteristics of the longitudinal chromatic aberration curve of the achromatic system is analyzed. Secondly, establishing the depth of focus(DOF) and wavelength relationship. The DOF is proportional to the wavelength and the square of working F#. Then, a working position is selected and the defocus amount between the working position and the focal position of each wavelength is calculated. Finally, the maximum allowable waveband range is determined by comparing the defocus amount of each wavelength at the working position with 2 times DOF. The method can be used to analyze the design waveband range of achromatic system, which is valuable for designing and testing of optical systems.

There is an increasingly urgent need for model attitude measurement technology in fields of urban modeling, aerospace, autonomous driving, etc. Among them, the point cloud registration algorithm is essential. The existing registration algorithms cannot simultaneously meet the requirements of high speed, high precision and large field of view. To this end, this paper proposes a registration algorithm, which combines normal distribution transform (NDT) and iterative closest point (ICP) to perform secondary registration on point clouds. An attitude measurement platform has been built and the LiDAR continuously obtains the point cloud data of the model. Multi-layered voxel and quasi-Newton method were used to accelerate the NDT algorithm， which is used to calculate the transformation matrix of adjacent frames. If the attitude change exceeds the threshold, ICP will be used with the initial solution from NDT. This method combines the high precision of ICP with the high speed of NDT, so that the dynamic model attitude measurement can be in real time under the premise of high precision, and it is suitable for a variety of attitude measurement scenarios with high precision, high speed and large field of view.

A photonic crystal fiber (PCF) consisting entirely of circular air holes based on hexagonal cladding and cross-shaped core structure is proposed. The transmission properties of the proposed PCF are simulated calculation by using TOPAS as the background material, the finite element method as the calculation method, and the circular perfectly matched layer (PML) as the boundary condition. The results show that very low transmission loss, including effective material loss (EML) with 1.04 × 10^-3 cm^-1 , the confinement loss with 2.3 × 10^-6 dB/cm, and the bending loss (when the bending radius is 1 cm) with 1.23 × 10^-17 cm^-1 can be got. When the proposed PCF under the optimal condition, extremely large effective area about 9.69 × 10¹⁶ μm² and flat dispersion about 0.46 ± 0.04 ps/THz/cm can be obtained, and the proposed PCF is in the single mode. Large effective area and ultra-low loss make the proposed PCF hold great future in low loss terahertz systems. Additionally, the proposed PCF with simple structure can be drawn by many methods such as the extrusion method.

In the past decade, the research on optical frequency comb and its applications has achieved rapid development, bringing revolutionary progress to the metrology field. Frequency stabilization and absolute frequency measurement of the CW laser through optical frequency combs is very important for establishing new length standards. A tunable near-infrared CW laser is phase locked to a commercial optical frequency comb referring to a Rubidium atomic clock for frequency stabilization. A home-made comb is phase locked to a hydrogen maser for measuring the absolute frequency of the frequency stabilized CW laser obtained. The procedure of frequency stabilization and absolute frequency measurement based on optical frequency combs is demonstrated and the uncertainty and stability of the frequency stabilized CW laser are estimated.

We present a novel backside-illuminated single photon avalanche diode (SPAD) which is compatible with standard CMOS technology. The structure of SPAD is based on p-i-n junction which is the first time to be used to backsideilluminated structure, thus enabling a significantly low dark count rate (DCR). In order to get better photon detection efficiency (PDE) in near-infrared , we optimized the junction width and thickness of the device. The structure of SPAD is designed by the TCAD Devedit tool, and some important characteristic parameters are extracted by the Atlas tool. We calculate DCR and PDE using the extracted parameters. At 5 V excess bias voltage, the DCR of 0.81 Hz/μm² is achieved at room temperature. The PDE at 5 V excess bias voltage is 20%. The fill factor is up to 53%. The DCR of the structure has reached the international advanced level.

It is very important for the safety of photothermal therapy to detect the temperature change of the interaction between laser and tissue during photothermal therapy. Using photoacoustic imaging can sensitively reflect the temperature distribution in the tissue. This paper proposes a photoacoustic temperature measurement method combined with quantitative absorption distribution. On the one hand, this method uses the temperature measurement method based on photoacoustic imaging to monitor the temperature change of the target area in real time; on the other hand, it quantifies the absorption distribution of the nanoprobe with the photoacoustic and photothermal effect in the target area. Thereby providing a feedback signal for temperature control during the treatment process, realizing precise control of the target area temperature and reconstruction of the absorption distribution of the target area nanoprobe. The study results verify the feasibility of this method. Compared with traditional quantitative methods, this article considers the dynamic changes of the target area temperature and provides treatment feedback. The feedback control guided by multiple parameters minimizes the damage to the surrounding healthy tissues, while improving the accuracy of reconstruction is helpful for the quantitative assessment of the disease.

In this paper, we build a two-dimensional (2D) simulation model of step doping InGaAs/InP uni-traveling carrier photodiode (UTC-PD) by TCAD and also compare its performance with PIN photodiode (pin-PD). The effect of doping concentration of the step doping absorption layer on the device performance is analyzed. As the doping concentration increases, the saturation photocurrent increases, but the 3-dB bandwidth decreases.

Seeker technology is the core of laser semi-active guidance. At present, laser semi-active guidance weapons are mainly used for large caliber ammunition such as shells, bombs and missiles, while small caliber ammunition is rarely used. It is an important development direction of laser semi-active guidance weapons. In this paper, a miniaturized high-precision laser azimuth detection system for laser semi-active guidance seeker is designed. On the basis of existing laser plate active guidance seeker technology, the working principle of quadrant detector is analyzed. A quadrant detector with photosensitive diameter of 3.04mm and photosensitive area product of 2.52mm² is selected to design a high-precision calculation based on FPGA which is different from sum difference algorithm Law. According to the actual needs, the design index of the optical system is summarized. An optical system with an entrance pupil diameter of 8mm is designed. The optical system is evaluated and analyzed. The propagation characteristics of the laser in the atmosphere are analyzed. A variable gain amplifier circuit with a gain adjustment range of 24dB is designed. In order to improve the signal-to- noise ratio and anti-interference ability, the relevant detection circuit is designed. The experimental results show that the average absolute error of the system is 0.09° which meets the design requirements.

Strip flatness is an important indicator of steel quality, and its detection technology has always been the focus of research at home and abroad. This paper proposes a non-contact online real-time measurement scheme for hot rolled strip steel. Our research is based on the laser triangulation method, which transforms the flatness detection into the strip surface height detection. In order to prevent errors caused by jitter during strip transportation, we have added a three-point measurement method. The flatness measurement system has carried out the system hardware design with FPGA and linear CCD as the core and the system software design with the laser spot positioning as the core. The basic technology realization process is based on FPGA as the main control and processing chip, collecting the laser reflection light signal of the measured strip steel surface through the optical system through the linear array CCD to obtain the strip surface height information. The collected signals are subjected to photoelectric conversion, filtering and amplification, and A/D conversion, and are transmitted through a network port based on UDP protocol. Finally, the spot center is positioned by comparing the selected threshold method to obtain important data for calculating the flatness information. In this study, a semiconductor laser with a wavelength of 450nm, a TCD1304AP linear CCD and an FPGA chip of the XC7A35T model produced by Xilinx were selected. In the range of 4 mm above and below the reference position, the measurement accuracy of the system can reach 10μm, which meets the measurement requirements of the measured strip elongation accuracy of 1% (when the elongation is 10~200 I) or 1 I (when the elongation is less than 1 I).

In order to identify the camouflage materials in military targets, this paper extracts multiple features to study the difference in optical characteristics between natural targets and man-made camouflage materials. Since Fresnel reflection can be regarded as a statistical description of scattering, this paper uses a multi-angle polarization measurement device to measure polarization and scattering characteristics. According to the physical meaning of the Mueller-Jones matrix, the expressions of amplitude ratio and phase retardation are extracted. Based on Pauli decomposition, new scattering similarity parameter formulas is defined. We discuss the curves of three characteristic parameters and analyze the difference between natural objects and camouflage materials. The experimental results show that the characteristic curves change significantly at Brewster’s angle, which clearly distinguishes the target from the camouflage material.

Total internal reflection imaging ellipsometry (TIRIE) is widely used in the field of the biological detection due to its high sensitivity and multi-detection capability. Traditionally, the ellipsometric measurement works under the null-off null condition which is insensitive to the small interface variations such as the electron density disturbance at the sensing surface. Thus, we analyze the response of the detected signals under the different working conditions to the ellipsometric parameter variations and optimize the polarization settings to further enhance the TIRIE response to the subtle interface variation in this paper. Furthermore, the relationship between the detected signal and the electron density disturbance is obtained, and the result shows that the detection sensitivity for the subtle interface changes is improved by one hundred times under the optimized working condition.

The realization of high-resolution imaging of images through scattering media has always been an important problem to be solved in the field. In this paper, our purpose here is to create a new framework that can realize the imaging through long-range scattering media. To do so, we establish a long-range scattering medium model, and use the model to generate simulated speckle pattern. In particular, we are designing a new neural network that is able to learn the statistical information found in the pattern of speckle intensity. The simulated speckle data were used as train sets for the neural network, and the learning rate of the SGD was 0.001, so that the model converged, which had good effects in the aspects of recovery time, imaging quality, mobility, convergence rate and so on. The peak signal to noise ratio (PSNR), Pearson correlation coefficient (PCC), structural similarity (SSIM) and other indexes were used to evaluate the performance of the convolution neural network in restoring images. Our neural network has achieved good results under this evaluation index from those results. PSNR value is 16.939, SSIM value is 0.842, and PCC value is 0.884, indicating that our new neural network model can realize long-range scattering media imaging and improve the imaging quality of scattering imaging.

Environment adaptability measurement, due to its important value of thermopile sensors research and direction of hot spot. Low cost, high-speed in measurement system and obtain long mean time between failure (MTBF),has become an urgent problem to be designed. In the paper, we analysis the test system and the parameter of accelerated aging. The system sets parameters to ensure the measurement data to be trust. And also, we design the electro magnetic compatibility (EMC) system to show the capacity of the disturbances. Polyethylene lens based the terahertz wave front modulation which is benefit the terahertz wave image technology. The measurement way to get the data has significant meaning for detection and quality to the thermopile sensors.

The morphology of high-voltage cable sealing layer has an important impact on the sealing characteristics. Aiming at the measurement problem of high-voltage cable sealing layer morphology, this paper uses a lattice laser to irradiate the target to form a laser lattice on the surface of the target, and then obtains the target image with a binocular polarization camera. The polarized light is used to overcome the influence of metal reflected flare, and then a pair of target images are matched. Then the parallax of each point is calculated. Finally, these points are used to reconstruct the point cloud to obtain the three-dimensional(3D) shape of lead sealing layer. The method in this paper provides a method for the measurement of the 3D shape of lead sealing layer, which is of great significance for the quality control of lead sealing layer.

The optical scene generator is used to generate the optical characteristics of real scenes and is an important means to test the optical imaging system. With the continuous improvement of the performance of optical imaging system, optical scene generator needs to generate optical scene with high frame rate and high resolution, which puts forward higher requirements for the transmission and display rate of scene. In order to meet the requirement of performance test, this paper proposes a transmission and display link of high-speed data transmission and dynamic scene display through digital micromirror device (DMD) based on Windows operating system platform. In terms of data transmission, the relationship between the scene resolution ratio and memory buffer is analyzed. By adjusting the size of send and receive buffer and window, the data transmission rate is increased by 32.82 times. Combined with multithreading technology, the transmission rate of 10 Gigabit network is stabilized at 8.8Gbps. In data receiving, length counting method is used to avoid the problems of packet sticking and packet splitting in TCP/IP. On the DMD display side, the total display rate was doubled by using USB3.0 port transmission, ping-pong buffer technology and binary pulse-width modulation technology. The experimental results show that the whole link transmission rate of the high-speed transmission and display system proposed in this paper reaches 395.5MB/s. It can realize the transmission and display of 8-bit gray scene with frame rate of 200Hz, resolution of 1920 × 1080.

The study of the interaction between laser and mouse brain tissue has important theoretical and practical significance for brain imaging. A two-dimensional simulation model that studies the propagation of light and heat transfer in brain tissue based on finite element has been developed by using the commercial finite element simulation software COMSOL Multiphysics. In this study, the model consists of three parts of 1) a layer of water on the surface of the brain, 2) brain tissue and 3) short pulsed laser source (the wavelength is 840nm). The laser point source is located in the middle of the layer of water above the brain tissue and irradiates the brain tissue. The propagation of light in brain tissue was simulated by solving the diffusion equation. And the temperature changes of gray matter and blood vessels were achieved by solving the biological heat transfer equation. The simulation results show that the light energy in the brain tissue decreases exponentially with the increase of penetration depth. Since the cerebral blood vessels have a stronger absorption on light compared with the surrounding tissues, the remaining light energy of the blood vessel in the cerebral cortex is ~ 74.86 % of the remaining light energy in the surrounding gray matter. In the process of biological heat transfer, due to more light deposition in blood vessels, the temperature of blood vessels is 0.65 K higher than that of gray matter, and the temperature of gray matter hardly changes. This research is helpful to understand the propagation of light in the brain and the interaction between them, and has certain theoretical guiding for the optical imaging of the brain.

The study of the relationship between the spectral characteristics of the photoacoustic signal and the shape and size of the absorber has important practical significance for image reconstruction. Using the commercial finite element simulation software COMSOL Multiphysics, a two-dimensional simulation model based on finite element was designed, which studied the relationship between the spectral characteristics of the photoacoustic signal and the shape and size of the absorber. In this study, the model consists of three parts: 1) water layer; 2) short pulse laser source (wavelength of 840nm); 3) gastric tumor tissue. The laser point source is located in the middle of the upper water layer. Simulate the propagation of light in the water layer by solving the diffusion equation. The temperature changes in biological tissues are obtained by solving the biothermal equation. When the absorber is irradiated by Gaussian pulses, due to the extremely short time, the absorber can be regarded as adiabatic expansion after absorbing energy, thereby generating ultrasonic waves. Using the finite element analysis method, the complex situation of photoacoustic imaging is transformed into the coupling of multiple physical fields and the numerical calculation of partial differential equations to obtain the photoacoustic signal. Fitting the simulation results shows that the spectral characteristics of the photoacoustic signal change regularly with the size of the absorber. The size of the absorber obtained in this paper has a power function relationship with the spectral intercept. The larger the size, the larger the spectral intercept, and the growth rate increases with the increase of the size. The size of the absorber and the spectral slope also have a power function relationship. The slope of the large spectrum is smaller, and the rate of change of the slope decreases as the size increases. At the same time, analyzing the photoacoustic spectrum of absorbers of different shapes also shows that absorbers of different shapes have their own characteristics. This research is helpful to understand the relationship between spectral characteristics and the shape and size of the absorber, and has certain theoretical guiding significance for image reconstruction.

We proposed a self-referenced technique for measuring the spatiotemporal characteristics of ultrashort pulses using the coherent diffraction imaging. This technique includes the wavelength spatial multiplexing coherent diffraction imaging measurement and the three-dimensional spatiotemporal amplitude and phase reconstruction. In experiment, we verified the feasibility of this technique by measuring a pulse from the femtosecond laser oscillator. Wavelength spatial multiplexing was realized by the combination of two-dimensional diffracted optical element and narrow-band-pass filter, and the amplitude and phase information of each wavelength was recovered by ePIE (extended Ptychographic Iterative Engine) algorithm. This technique can measure the three-dimensional spatiotemporal amplitude and phase information of ultrashort pulses with high resolution and simplicity. In the future, it is expected to be an effective method for the comprehensive monitoring of the spatiotemporal optical field of ultrashort pulse lasers, and will be helpful for the laser performance improvement.

According to the comprehensive test requirements of commercial and self-developed marine sensors carried on the Smart Float, an ocean sensor integrated interface platform is developed, which is composed of underwater connection unit and shore-based control center. The underwater connection unit contains the main controller, serial port server, Ethernet switch, and remote transmission equipment, etc. and it communicates with the shore-based control center through a twisted-pair or armored cable. The underwater connection unit is designed to implement the functions of power management, sensor electric current monitoring, environment temperature monitoring, and data self-storage, while the shore-based control center is designed for remote control, curve drawing, and data storage. The offshore test results indicate that our design provides an efficient and stable platform to simulate the Smart Float, ROV and HOV interfaces, and carry out the integrated connection test for the marine sensors. It demonstrates the outstanding ability for the comparison of self-developed sensors and commercial sensors, as well as the scientific application of carbon storage and oxygen capacity

Laser-assisted machining in-situ technology is an emerging hot spot in the processing field. The technology not only has an excellent performance in processing Cu, Al, and other tough metals but also is an effective method for surface treatment and microfabrication of difficult-to-process materials such as engineering ceramics, high-temperature alloys, and composite materials. And technology has an excellent performance in improving machining accuracy, surface quality, tool life, machining efficiency, and so on. Firstly, the principle of the technology is explained, followed by the introduction of the research progress of scholars at home and abroad in recent years from the perspective of laser in-situ auxiliary multiple different processing methods, finally, the existing problems and future development direction of the technology is summarized and prospects.

In order to accurately and non-destructively identify the true or fake of blood, the photoacoustic spectroscopy technique was used in this paper. Meanwhile, a kind of custom-built photoacoustic spectroscopy detection system was established. In this system, a 532nm pumped OPO pulsed laser was used as the excitation source, and a focused ultrasonic detector with central echo frequency of 2.5MHz was used to capture the photoacoustic signals of the blood samples. In experiments, five kinds of different blood samples, i.e, three kinds of animal blood, and two kinds of fake blood (props blood and red ink) was used as the experimental blood samples. The sample groups were 125, the train samples were 100 groups, the test samples were 25 groups. The photoacoustic signals and peak-to-peak values of all blood samples were obtained. To distinct accurately the blood, two different algorithms, i.e,, PCA-KNN, and BP-GA were used. The photoacoustic peak-to-peak values were used as the input data. For PCA-KNN, the distinction correct rate of five kinds of blood is 96%, which is larger than that of the KNN (88%). For the BP-GA, the distinction correct rate of five kinds of blood is 100%. Therefore, the photoacoustic spectroscopy combined with artificial intelligence algorithms have the significant values in the distinction can classification of blood

We propose a terahertz metalens based on Huygens’ metasurface which can realize the focused field enhancement compared with the single-layered metasurface. The metalens consists of two-layered well-arranged metallic C-shaped split-ring resonators array separated with the dielectric layer. After investigating the relationship between the transmission characteristics and the geometrical parameters of the metasurface, we demonstrate that the Huygens’ metasurface can efficiently enhance the transmission amplitude while inducing the phase gradient within the supercell. Due to higher transmission amplitude of the Huygens’ metasurface, the electric field of the focus is enhanced 117% at 0.8 THz. Our results may offer a new avenue to design efficient metalens, which is promising in developing metasurface-based integrated devices for the terahertz imaging.

Avalanche photo-diode (APD) is often used as the core photo-detector in the receiving end of 3D imaging LIDAR. As the photo-sensitive area of the highly sensitive APD is limited, the receiving field of the optical receiver is limited. Therefore, it is necessary to expand the receiving angle and make the spot size smaller than the photo-sensitive area of the APD used. After deducing the relation between the deflection angle and the receiving field angle of the micro electro-mechanical system (MEMS) micro-mirror, an improved three-piece lens and a synchronous optical receiving method based on the MEMS micro-mirror are proposed to expand the receiving field of view from 5.7" x 5.7" to 36"x 36". On this basis, the front and rear lens combination of MEMS lens is simulated with ZEMAX software, and the light reflected by the MEMS micro-mirror is simulated and received. The spot size obtained is suitable for the APD photo-sensitive surface used.

In this paper, a high efficiency method to generate vector beam based on a single liquid crystal spatial light modulator (LCSLM) is proposed. In this method, the system used to generate vector beam adopts a collinear configuration which makes the system more stable and the core components of the system include a half-wave plate, a reflective phase-only LCSLM and a quarter-wave plate. With the proposed system, the polarization states distribution of output beam could be modulated by controlling the phase pattern displayed on LCSLM and the relative intensity of the two orthogonal components in the beam reflected by LCSLM. We conducted a theoretical analysis of the method and demonstrated the validity and feasibility of the method experimentally. The experiment results are highly consistent with the results obtained through theoretical simulations.

In order to improve identification rates (IRs) of signal recognition for optical fiber perimeter defense systems, a novel signal recognition method based on the fast dynamic time warping (FastDTW) algorithm and nearest neighbor criterion is proposed. The distributed optical fiber sensing system based on an in-line Sagnac interferometer is employed as a simulated perimeter defense system to acquire three different kinds of sensing output signals. The signals are divided into several signal segments according to their categories and selected as reference templates and test samples, respectively. The FastDTW can calculate the optimal warping path distance between the test sample and each reference template. The signal recognition results are obtained according to the nearest neighbor criterion. The experimental results show that the average IR of the three kinds of sensing signals is above 99%. The proposed recognition method does not need special training process, hence is simple, and easy to implement. It can achieve a high identification rate under small sample condition which provides a new approach for the signal recognition of optical fiber perimeter defense systems.

In this work, we fabricated millimeter-sized perovskite single crystal and applied it into photodetectors. The yellowphase perovskite crystals can be obtained through solvent circulation and evaporation, which shows smooth surface and square-shape, and emits green color under 365 nm UV excitation. The photodetector based on it displayed larger response speed and high spectral responsivity.

In order to accurately evaluate the dynamic performance of inertial devices, this paper proposed an angular vibration test system and method for inertial devices based on heterodyne interference technology. This system is mainly composed of the angular vibration excitation device and the angular vibration measurement device. By installing an angular reflector on the swing table, the dual-frequency laser interferometer (DFLI) can measure the real-time angle value of the swing table, then obtain its amplitude-frequency characteristics with the Fast Fourier Transform algorithm . The experimental results show that the test system can measure angular vibrations exceeding 1000 Hz. Furthermore, the frequency bandwidth of an interferometric fiber optic gyroscope (IFOG) fabricated in our laboratory is evaluated by the angular vibration test system aforementioned, and its cut-off frequency is measured as 375 Hz. Finally, a comprehensive theoretical analysis has been implemented to investigate the uncertainty factors in the DFLI of this system.

Space Gravitational-wave (GW) detection requires the establishment of an ultra-long-range interplanetary laser communication link. Compared with general inter-satellite laser communication, the power emitted by the laser is relatively small, and only a small part of the power is used to achieve communication. Therefore, higher requirements for communication reliability are put forward. Optical antenna vibrations, on-platform vibrations, and interstellar relative motion can shift the alignment optical path, causing aiming errors at the transmitter and receiver to affect the communication link, while laser wavelength, transmission distance, transmitter and receiver design parameters, and system noise can also have complex effects on the communication link. In this paper, we propose a reliability analysis method for interplanetary laser communication links based on transmission parameters. The basic model of the interstellar laser communication link is first developed in terms of the average received optical power of the detector, and the corrected Rayleigh distribution is used to describe the aiming error. Then, the relationship between the transmitting and receiving signals is analyzed to give a model of the Bit Error Rate (BER) of the communication system, and the link reliability is measured by the error probability. Finally, the effects of changes in parameters such as emitted beam divergence, vibration, communication rate, communication distance, and receiving antenna aperture on the error probability are analyzed, and the optimal beam divergence width is obtained by calculation. Simulation experiments show that the emitted beam scatter and aiming error angle are the main factors affecting the performance of interplanetary laser communication in the space GW detection laser link. Choosing the optimal beam dispersion angle yields the lowest error probability and reduces the requirement for transmitting power. Static deviations in the aiming error angle can reduce the reliability of the link. In this paper, a method for analyzing a system of transmission parameters to improve the reliability of interstellar laser communication links is developed, which provides an effective means for the analysis and design of communication links for space GW detection.

Tandem pumping has been proved as an efficient approach to realizing high power Yb-doped fiber lasers and amplifiers. Currently, the most widely used pump laser is operating at 1018 nm, where the relatively small absorption cross section of Yb-doped fiber inevitably leads to long fiber length for sufficient pump absorption. The long active fiber, however, would significantly lower the stimulated Raman scattering threshold, limiting further power scaling. Therefore, theoretical analysis is carried out with the aim of shortening the Yb-doped fiber length in the tandem pumping scheme by employing pump lasers with shorter wavelength, i.e. 1007 nm and 1010 nm in this work, and the simulation results indicate that higher overall efficiency and better signal-to-noise ratio (SNR) could be obtained in a high-power fiber amplifier with these shortwavelength pump lasers. Further simulation suggests that fiber lasers operating at 1007 nm with high efficiency and high SNR can be obtained by optimizing the cavity parameters.

As a non-invasive, targeted and non-radioactive technology applied to tumor treatment, photothermal therapy is increasingly used in the clinical treatment of tumors due to its high cure rate and few side effects. In order to obtain a better photothermal treatment effect in the actual treatment process, the temperature distribution of the tissue to be treated must be monitored and controlled to prevent unnecessary tissue damage caused by the treatment. Therefore, the photothermal probe and precise control of the treatment temperature become the key to solving the problem. In this paper, a nanoprobe with strong photoacoustic and photothermal properties in one area of near-infrared is designed. At the same time, a photothermal treatment system is designed and combined with nanoprobe for research. This study designed human tissue simulation experiments and found that compared to the case without probe assistance, the photothermal therapy system based on photoacoustic and photothermal probe assistance can achieve temperature control with a temperature error of 1°C , and the temperature control adjustment time has been shortened by 40%, and the overtreatment injury has also been effectively suppressed. More importantly, it is possible to greatly reduce the complexity of the photothermal treatment process in practical applications without the artificial control of continuous laser power. The experimental result shows that the intelligent photothermal treatment method based on the photoacoustic and photothermal nanoprobe is a feasible candidate for tumor treatment and has a good application prospect in the field of tumor treatment.

In this paper, we propose a multi-domain quantum key pool (QKP) capacity adaptive supplement scheme based on balance between key resource and routing hop in multi-domain QKD-ON, and we conduct the simulation and evaluate the performance of the proposed scheme in terms of service blocking probability and utilization of key resource. Results show that the algorithm can reduce service blocking probability.

In order to obtain the terahertz detection signal as accurately as possible, a numerical simulation tool for terahertz signal reception is developed in this paper. The numerical simulation tool with the full-wave finite-difference time-domain (FDTD) method in three dimensions (3D) that couple multi-physics together is capable of getting the Terahertz detection signals. The carrier distribution effect of the incident femtosecond laser interacting with terahertz on the detector is analyzed briefly, and the simulation tool is validated by comparing the incident terahertz signal with the detected terahertz signal by using the low temperature growth GaAs substrate. The results show that the simulation tool developed in this paper is of great significance to the terahertz detection of micro-structure photoconductive antenna.

Publisher’s Note: This paper, originally published on 28 February 2021, was replaced with a corrected/revised version on 10 May 2021. If you downloaded the original PDF but are unable to access the revision, please contact SPIE Digital Library Customer Service for assistance.