This PDF file contains the front matter associated with SPIE Proceedings Volume 12760, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

We demonstrate a diode-pumped SESAM mode-locked Yb:(Y,Gd)AlO₃ laser delivering soliton pulses as short as 28-fs at 1063 nm with an average output power of 21 mW. The maximum average output power is scaled to 135 mW for a pulse duration of 37 fs.

We created and measured properties (the Verdet constant, absorption coefficient, thermooptical constants Q and P relevant to thermally induced depolarization and thermal lens effect) of promising magneto-optical Terbium-Aluminium Garnet (TAG) and Terbium-Hafnium Pyrochlore (THP) ceramics. It is shown that TAG ceramics made by solid-state reaction sintering has smallest absorption coefficient and could work as magnetooptical element in Faraday Isolator (FI) with a kW-class laser power providing 30 dB isolation ratio. So, TAG based Faraday rotators can be successfully used in laser system with high average and peak power.

To enhance the correlation in the orthogonal directions, a polarization self-modulation scheme with an intra-cavity quarter wave plate in a coaxial pumping orthogonally polarized laser was proposed. This quasi-isotropic cavity was compared with the traditional scheme in terms of the differences in the oscillation between dual components and the intra-cavity eigenstate distribution was obtained. Both theoretical and experimental results indicated that modes were effectively locked in TE and TM directions and dual-eigenstates output was achieved, which provided a half-free-spectrum-range frequency difference in ±45° directions. Q-switching and dual-wavelength-operation did not affect the polarization self-modulation process.

A concept of compact, scalable and reliable solid-state amplifier based on thin slab is proposed. It combines the following features: single pass pump and signal propagation without internal reflections; use of a gradient doped thin-slab AE; beam guiding effect pre-compensation. The direct passage of the radiation allows to obtain a high quality of the beam (M2⪅1.4). Thin slab geometry and gradient doping provide excellent heat dissipation and low heating (30 °C at 500 W pumping power). The amplification of stretched and pre-amplified femtosecond radiation reached 3.6 (with input of 6 mJ) at a pump power of 500 W, so output energy was 22 mJ at 1.5kHz. A further increase in the output energy is possible according to calculations, up to 100 mJ, which is limited by the breakdown threshold of the output end at a pump power of 1 kW.

The Laser Diode (LD) end-pumped solid-state lasers with excellent output characteristics are extensively used in many fields. The thermal effects of the laser crystal are one of the key factors preventing the laser from achieving high-quality output. In this paper, the thermal effects of a laser at 1 kHz repetition rate were explored by developing a three-dimensional thermal model of an end-Quasi-Continuous Waves (QCW) LD pumped Nd: YAG crystal. Considering the radial and axial heat conduction of the laser crystal, the transient temperature field within the crystal was numerically calculated using a seven-point Finite Difference Method (FDM). The transient thermal effects of the composite crystal were compared with those of the non-composite crystal. The effects of different parameters on the transient thermal effects of the composite crystal were discussed in detail. This simulation work is believed to guide the design of thermally stable cavities for lasers operating at muti-kHz to attain favorable laser characteristics.

In order to obtain a passively Q-switched sub-nanosecond microchip laser with a low pulse jitter of less than 10 ns, a scheme of injection-seeding stable nanosecond laser pulses was designed. The pulse timing jitter of the passively Q-switched laser was improved from μs-level to ns-level with the seeding pulse energy of around 70 μJ. Based on experimental measurements, the dynamic process of pulse locking by varying the seeding pulse energy was discussed. The locking threshold affected by the peak pump power and time delay (Δt_Q) between the initial passively Q-switched laser and seeding pulses was also analyzed.

We fabricated a diode array side-pump, passively Q-switched laser for our laser rangefinder system. The 25 mm linear cavity laser was designed with a rectangular Yb:Er:glass rod as the active element, and a Co:spinel plate as the saturable absorber. The active element was pumped with two quasi-CW 940-nm diode arrays. The pump-to-laser beam overlap was optimized by attaching the Fast Axis Collimator (FAC) lens on the diode arrays. The design for heat transfer from rod surface to the ambient medium is also considered in this report. Our laser operates stably at the wavelength of 1535 nm. The laser pulse energy and pulse width are 1.5 mJ and 4.6 ns, respectively. The repetition rates are tunable from 1 Hz to 10 Hz.

We describe the photo-injector drive laser system for the Shanghai high-repetition-rate XFEL and Extreme light facility (SHINE). A fiber chirped pule amplification system is designed to produce high-repetition-rate high-energy infrared picosecond pulses and a subsequent fourth-harmonic generation system is employed to produce deep ultraviolet picosecond pulses. The latest development on key performance parameters of 1 MHz, infrared and deep ultraviolet picosecond pulses for the SHINE photo-injector drive laser system will be presented.

Compressing high-energy laser pulses to a single cycle will break the current limitation of super-scale projects and facilitate future Exawatt lasers. However, the lack of ultra-broadband gratings capable of supporting single-cycle pulse stretching and compression is a core problem that cannot be overcome. Recently, we solved this problem and developed gratings with the broadest bandwidth (broader than 400 nm) that can support near-single-cycle laser pulses (about 4 fs). A 200 mm (Length) ultra-broadband grating is being fabricated supporting a single-cycle terawatt-level prototype. Meanwhile, the 1600 mm (Length) fabrication campaign is underway and will be completed in 2024–2025 at SIOM, facilitating the single-cycle Exawatt lasers.

Self-referenced spectral interferometry is a widely used technique due to the advantages of spectral interference. However, the inherent nature of its self-referencing confines its measurements predominantly to pulses nearing the Fourier-transform limit. In this study, we introduce an improved self-referenced spectral interferometry method capable of characterizing large, chirped pulses. Based on this method, we successfully characterized a pulse with a duration of 87 fs, exceedingly twice the Fourier-transform-limited pulse width and obtained a temporal profile consistent with that measured using frequency-resolved optical gating.

This paper investigates a segmented mirror splitter system for beam combiners. Most of previous work lack the analysis of various types of errors in beam combiner. Instead, we analyze the influence of varying distortion levels and synthesis pulse quantities on the coherent combining efficiency. In particular, we analyze the efficiency losses caused by various factors such as the beam splitter’s splitting ratio, phase mismatch, power imbalance, polarization, spatial misalignment, and pointing error of the beam combiner. Accordingly, an analytical formula for assessing coherent combining efficiency is derived, providing a theoretical foundation and guidance for the design and optimization of high-power beam synthesizers. In general, this study could serve as a valuable reference for enhancing the performance of beam combiners in real-world applications.

We report on the optimization of femtosecond-pulse inscribed arrays of short randomly spaced FBGs for Raman lasing in multimode GRIN fiber pumped by highly multimode (M² ~34) 940-nm diodes. The fabricated 1D-3D FBG arrays used as a complex output mirror together with input highly reflective FBG provide random lasing of the Stokes beam at 976 nm with output power around 30 W. The optimization of array structure results in beam quality improvement to M² ⪅2 and the linewidth narrowing to 0.1 nm to 0.2 nm that is better than that for long regular FBG of comparable reflection. Potential of such cavity structure for further parameter improvement and its practical applications are discussed.

Through this paper, we describe the method leading to the estimation of the uncertainty. We aim to give an estimation of the uncertainty on the frequency peak by Brillouin Scattering Stimulation. It corresponds to the speed of phonons inside a material excited by a 532nm wavelength laser. The guideline follows the Guide to the Expression of Uncertainty in Measurement and its estimation is of 0.26% on the Brillouin frequency peak at 15.70 GHz for polymethyl methacrylate (PMMA).

Ultra-precise timing technique with low-power lasers holds immense significance in numerous advanced applications. Presently, the nonlinear-optics-based timing method falls short in delivering sufficient resolution under low-power conditions, while the intricate setup of the linear heterodyne timing technique makes it hard to implement. In this article, based on the AOM timing detection principle, an attosecond-precision balanced timing detector is firstly evaluated. By utilizing time and frequency multiplexing configuration, an electronic-noise-suppression timing detector is then demonstrated. Given the simplicity, low power consumption, and exceptional timing precision of our approach, these two linear-optics-based timing methods hold broad applicability in the realms of metrology, ranging, and synchronization.

Using retroreflectors in the laser cavity can enlarge the laser misalignment tolerance significantly and even realize alignment-free operation over a dynamic range. We summarized the optimization criteria for the alignment-free laser with the scheme including several Cat-Eyes Retroreflectors (CER). The telescope system and coupled-resonator scheme were utilized to alleviate the beam divergence over the long working distance and decrease the laser intensity on the optical path between the transmitter and receiver to improve laser safety, respectively. Through theoretical analysis, we recognized that two types of serious aberrations, spherical aberration and field curvature, were the essential factors that limited the laser operation dynamic range. After meticulous optical design to compensate the aberrations, a working distance range of 1 m to 5 m with over 5 W output power was demonstrated. Meanwhile, a receiver field of view (FoV) of ±30° and a transmitter FoV of 4.6° (corresponding to the receiver transverse movement of 40 cm) at a 5 m working distance were also obtained with multi-watt power output. We experimentally realized efficient laser operation over a large dynamic range, which paves the way for laser adaptive wireless power transfer/communication applications.

A new dual-core fiber coupler is designed to realize the coupling of pump light from pump fiber to gain fiber to achieve the amplification of signal light. The optical coupler comprises three parts: pump coupling and laser amplification section, proportionally reduced size section, and single-mode signal transmission section. The pump coupling and laser amplification section is composed of pump optical fiber A and anti-resonant signal fiber B. For the coupling part, the coupling ratio of pump light LP01 mode is 97.8%, and the coupling length is 2.97 m. For the designed fiber coupler, low transmission loss can be achieved for both 976 nm and 1064 nm at the pump coupling and laser amplification section, while single-mode, low transmission loss at 1064 nm, and high loss at 976 nm for residual pump stripping are obtained at the single-mode transmission section.

In this work, the effect of 2 μm core pump wavelength on the quenching behavior of 3.5 μm Er-doped ZBLAN fiber laser are experimentally investigated in detail. Pumped at an optimized wavelength of 1990 nm, a maximum 3.47 μm output power of approximately 7.2 W was obtained with 6.5 m Er-doped ZBLAN fiber, where the slope efficiency (with respect of launched 1990 nm pump power) and overall optical efficiency are 36% and 26.5%, respectively. Numerical simulation was implemented to reproduce the experimental results and determine the cross section of ESA via a theoretical fitting.

We demonstrated a high accuracy prediction of the fiber laser output parameters by using a feed-forward neural network. We explored both the gain and spectral filter parameters to test the prediction performance of the neural network and realized the mapping between cavity parameters and laser output performance. We also investigated how the number of hidden layers could influence the accuracy of prediction. Based on the results, the output spectrum and temporal pulse profiles can be predicted with high accuracy in various fiber laser designs. Our work paves the way to intelligent laser design with ultimate autonomy.

We investigate generation regimes of dispersion-managed solitons depending on the net cavity dispersion of the all-fiber polarization maintaining laser. Dispersion changes from anomalous region, where shortest pulses are achieved, crossing zero to normal values, where high pulse energy can be reached, provides flexibility of pulse output parameters for different possible applications. One of which is a pump of epitaxial single-photon source where it was tested as an alternative to Ti:Sa laser. The experimental results confirmed identical to Ti:Sa laser efficiency while retaining high purity of the single-photon source.

A single-cavity triple-comb all-fiber laser is proposed by wavelength/polarization multiplexing. A variable optical attenuator is introduced to equalize the 1530-nm and 1550-nm gain profile of erbium-doped fiber for dual-wavelength pulses. Their repetition rate difference reach kHz level. Meanwhile, by further adjusting the intracavity polarization state, polarization-multiplexed dual-comb pulses with tens-of-Hz repetition rate difference in the 1550-nm gain region are obtained. The more than one-order-of-magnitude difference between the maximum and minimum repetition frequency difference and qualified passive mutual coherence of triple-frequency pulses is highlighted. These results indicate a highly potential triple-comb source for multiple-comb metrology such as triple-comb ranging and frequency measurement and so on.

In recent years, the diversity of transition metal dichalcogenides (TMDs) have made them widely used in fiber lasers for the saturable absorption effect. Zirconium ditelluride (ZrTe₂), as a member of TMDs, has a high anti-damage threshold, and it exhibits excellent and controllable photoelectric performance due to the anisotropy of the band structure. In this paper, we prepared a ZrTe₂ saturable absorber film for passively mode-locking operation in an erbium-doped fiber laser and obtained an optical pulse output with a central wavelength of 1564.4 nm and a repetition frequency of 5.81 MHz. The spectral 3-dB bandwidth is 0.51 nm, the pulse width is 2.98 ps, and the signal-to-noise ratio of the fundamental frequency is 60 dB. These results show the potential of ZrTe₂ as a new saturable absorber material for generating ultrashort pulses, and this is the first demonstration for mode-locked fiber lasers based on ZrTe₂ material.

A 976nm fiber-coupled diode laser module based on stepped prisms and polarization beam combiner is proposed in this paper to solve the mismatch of beam quality in both directions of diode lasers. The beam size was compressed on the fast and slow axis without using a prism stack for beam shaping. Based on that, a laser stack of eight mini bars was coupled into a fiber with a core diameter of 200 μm and a numerical aperture of 0.22. The simulation results show that the output power of the fiber-coupled module is 597 W, the brightness is almost 12.5 MW/(cm² ·sr), and the optical-to-optical conversion efficiency is 93.28%. The fiber-coupled module proposed in this paper can not only achieve high power outputs but is also widely used in the fields of material processing and industrial.

Incoherent laser beam combining based on signal combiners is an effective method to significantly increase the laser power. Although many high power signal combiners have been reported, most of these combiners have seven or less input ports. In this paper, a 19×1 signal combiner is fabricated based on tapered fiber bundle technique including optical fibers bundling with capillary, fiber bundle tapering, cutting, and fusion splicing to the output fiber. The input fibers of the combiner are 14/250 μm-core/cladding optical fibers, and the output fiber is a 100 μm-diameter-core multimode fiber. The signal combiner is tested with eight 1500 W fiber laser modules, and 11.55 kW output power is obtained. The beam parameter product is 3.83 under 2 kW laser output. The temperature rise of the signal combiner is measured under passive heat dissipation condition at different laser power outputs, and the thermal slope is calculated to be 1.56 °C/kW. This 19×1 combiner has the potential to be used in a 30kW-level or even higher power fiber laser system.

We calculated the pulse shape of Ne-like Ar 46.9nm x-ray laser which population inversion is from the electron impact excitation. We used the Cowan codes to calculate the level energy, radiative transition rate and oscillator strength of the 2s²2p⁵3p, 2s²2p⁵3s and 2s²2p⁶ configurations. With the electron impact excitation (de-excitation) rate coefficients, the rate equations are established. Approximating the time dependent curve of electron temperature and density as a square wave, the time dependent curve of populations and 46.9nm laser photon number is calculated. Thus, the pulse shape is obtained. Finally, we analyzed the influence of gain duration, electron temperature and density on the pulse duration.

In this paper, we propose that a Chirped and Tilted Fiber Bragg Grating (CTFBG) can be fabricated in the 14um-core fiber to suppress SRS to achieve a higher-power single-mode fiber laser. The results show that the CTFBGs can suppress the SRS about 25 dB, and the power of the 14um-core single-mode fiber laser can be improved to 3 kW. The M² of the laser is less than 1.20. The CTFBGs are fabricated with an excimer laser and the heating rate of the recoated CTFBGs are less than 0.01 °C/W. The research results have certain significance for suppressing SRS in high-power single-mode fiber lasers with CTFBG for improving the output power.

We demonstrate a Q-switched mode-locked Er-doped fiber laser using an all-fiber grade-index multimode fiber-based modulator which generates dark-bright pair between bright pulse sequences and alternate bright and dark pulses. A section of dispersion compensation fiber (Nufern UHNA4) considered as a candidate normal group victory dispersion fiber is used to adjust the net dispersion of cavity. At a pump power of 410 mW, evident Q-switched instability modulating mode-locked bright pulses are observed, and the duration of Q-switched envelope changes from 1.8 μs to 8 μs along with the variation of power. Changing the state of polarization controller, the mode-locked bright pulse train is tuned to dark pulse train with reducing the duration of Q-switched envelope to 1.2 μs. What’s more, dark-bright pair between bright pulses train and alternate bright and dark pulses are also observed under second harmonic operations with suitable PC states. Coupled complex Ginzburg-Landau equation, field coupling model for propagation in multimode fiber, and fiber nonlinear effects are provided to reveal the underlying principles of the transition of these pulse trains. Because of the principal modes and filtering effect in multimode fibers, the formation and stable propagation of the dark-bright pair are precisely achieved. At the same time, the physical mechanism behind the unusual pairing of dark and bright pulses is that under certain conditions, cross-phase modulation can counteract the time extension of optical pulses caused by the combination of self-phase modulation and normal dispersion. Thus, the cross-phase modulation induced chirping on dark solitons enables dark-bright pair between bright pulse sequences to coexist.

We present the comprehensive elucidation of an exclusively fiber-based nanosecond Master Oscillator Power Amplifier (MOPA) laser system, integrating a 100-μm-core ytterbium-doped fiber within the primary amplification stage and a 300- μm-core Quartz Block Head (QBH) delivery configuration. The laser system hinges upon a diode laser seed, yielding a pulse train with pulse duration of 50 ns and repetition rate of 30 kHz. Consequently, the resultant pulse profile exhibits a final full width at half-maximum (FWHM) of 8.8 ns, concomitantly achieving a pinnacle power output exceeding 1.5 MW. The average power output attains a magnitude of 456 W, concomitant with a maximal pulse energy of 15.2 mJ. These findings collectively underscore a noteworthy advancement in both average and peak power outputs, notably within the context of narrow pulse durations and low repetition rate regimes.

High power fiber lasers are widely used in industrial processing such as cutting and welding. A high-power single-mode fiber laser emits laser beams in a single transverse mode (fundamental mode), exhibiting near-diffraction-limited laser transmission characteristics. It can converge into smaller light spots and achieve higher power density. Therefore, it serves as a preferred laser source for precision machining tasks involving high-speed and high-precision cutting, such as cutting of high-reflective materials, welding of dissimilar metal materials, and other industrial precision processing scenarios. It can also serve as a basic module for achieving higher laser power output with good beam quality through beam combining. The power scaling of a single fundamental mode fiber laser is limited by factors, such as transverse mode instability and nonlinear effects. This article introduces multi-stage amplified structures that employs wavelength-stabilized 976nm pump diodes, homemade fiber gratings, cladding light strippers and pump combiners. With the high-performance homemade Raman scatter suppressor and a well-designed fiber coiling approach, the high-order modes and Raman light in fiber laser are suppressed effectively. A single fundamental mode continuous laser has been achieved stably at maximum output power of 3 kW, optical slope efficiency of 79.97 %, M² factor of 1.05, and Raman suppressed ratio of ≥ 35dB. Further improvements can be made by increasing the pump source power and enhancing the filtering efficiency of the Raman scatter suppressor, which is expected to enable higher single fundamental mode power output.

The significance of researching and developing thermal stabilization systems for end-pumped amplifiers in high-power lasers is evident in modern optical and laser technology. There are several key factors driving this importance. Firstly, high-power laser systems have pivotal applications across diverse fields, including science, medicine, industry, and defense. Secondly, high-power laser systems generate substantial heat, resulting in thermal effects that impact their optical stability and efficiency. Thirdly, the implementation of optical thermal stabilization systems enhances the performance and durability of high-power lasers. In summary, the research and development of optical thermal stabilization systems for end-pumped amplifiers are crucial endeavors in ensuring the stability, efficiency, and reliability of high-power laser systems.

When laser light propagates though the atmospheric turbulence, it would be affected by the fluctuation of atmospheric turbulence. Especially in harsh environments, atmospheric fluctuation will cause serious dispersion of the light spot, which has a serious impact on the energy utilization rate of laser eavesdropping system. This study focuses on the relationship between temperature fluctuation and energy utilization rate of laser eavesdropping system via the numerical simulation. Taking the temperature pulsation meter type QHTP-2 as the example, the theoretic derivation and numerical simulation are conducted. The result shows that the average energy utilization rate decreases rapidly with the increase of the standard deviation of temperature, and the 15% measurement uncertainty of the temperature pulsation meter will cause the energy utilization rate fluctuation between -6% and 8%. It provides us with a valuable criterion for laser eavesdropping system design.

Dual-Comb Spectroscopy (DCS) is a novel high-performance spectral measurement technology. However, conventional DCS systems often rely on optical frequency comb seed sources, which have limited output power and are not capable of withstanding the substantial losses encountered during on-site detection. Additionally, their spectral range is often narrow and may not be suitable for the target gases. In this work, we demonstrate a high-power, wide-spectral-range dual-comb spectroscopy measurement system for on-site spectral detection. The system comprises two optical frequency combs with close repetition rates, utilizing erbium-doped fiber amplifiers and dispersion compensating fibers for power amplification and broadening of the spectrum. We successfully detect absorption spectra of multiple gases, demonstrating good agreement with the simulated spectrum from the HITRAN standard database. The spectral resolution can reach sub-picometer-level (approximately 0.45 pm). This work shows the potential of dual-comb spectroscopy technology transitioning from laboratory research to industrial on-site applications.

Utilizing Wireless Optical Power Transfer (WOPT) at extended wavelengths offers a secure means of long-range wireless power transmission. An innovative approach known as Resonance Beam Charging (RBC) has been recently introduced, employing retroreflectors for simplified alignment. This investigation presents a WOPT system incorporating an Erbium-Doped Fiber Amplifier (EDFA) that functions at 1550 nm. We have summarized and compared the reflectivity and transmissivity of a spherical ball lens retroreflector when interacting with the incident beam to optimize power transfer. The system yields an electrical power output of 0.5 Watts, covering a span of 25 meters. The experiment scrutinizes a gallium antimonide photovoltaic cell, achieving a notable 23 percent conversion efficiency from optical to DC-electrical energy. In the final phase, a mathematical assessment is conducted to determine the safe power levels for human skin and eyes, adhering to the Laser safety standards' Maximum Permissible Exposure (MPE) thresholds. The receiver model can potentially enhance the illumination area on the photovoltaic receiver, thereby increasing its efficiency. To validate the performance of the proposed model, a GaSb PV cell is used in the scheme.