Stress in diamond crystals is a critical factor affecting Raman gain and the polarization state of the output Stokes. This study systematically investigates the multi-field coupling among residual-stress-induced birefringence in diamond, initial pump ellipticity, and stimulated Brillouin scattering (SBS). By combining theoretical simulations, division-of-focal-plane polarization imaging, and Raman laser experiments, we elucidate the mechanisms responsible for the stepwise evolution of the Stokes polarization direction. In high-stress regions, birefringence-induced phase distortion dominates the polarization dynamics, leading to abrupt polarization switching. In low-stress regions, SBS acts as a parasitic loss channel that forces polarization-mode transitions and limits power scaling. The results further confirm that even slight pump polarization perturbations can degrade the Raman output polarization state, reduce the effective gain, and increase the laser threshold. These theoretical and experimental findings provide practical guidance for overcoming performance bottlenecks in diamond Raman lasers, screening high-quality crystals, and developing efficient coherent light sources with precisely controllable polarization states.

Picosecond ultraviolet lasers are extensively utilized in precision manufacturing and material processing, where system designs prioritize longevity and stability. However, the emphasis on durability and simplicity-exemplified by extra-cavity configurations with LBO crystals-often compromises the overall conversion efficiency, underscoring the need for further optimization. We developed a simulation model based on the spatial distribution characteristics of second harmonic generation (SHG) efficiency to guide the design of an efficient third harmonic generation (THG) system. We developed a simulation model that reveals the functional relationship between the fundamental peak power and the optimal beam diameter. Based on the simulation results, we optimized the design of a highly efficient third harmonic generation system. Consequently, we achieved a conversion efficiency of 17.89% for wavelength conversion from 1030nm to 343nm. The design integrated disk regenerative amplification and single-crystal fiber technologies for the first time, delivering an ultraviolet output with an average power of 30.2W. This method advances the third harmonic generation efficiency and offers new pathways for compact, high-performance picosecond ultraviolet laser development in scientific and industrial domains.

A high-energy, high-beam-quality, all-solid-state, dual-wavelength picosecond laser is designed for spatial-target ranging. This system features a fundamental-frequency laser with a bandwidth of 0.3 nm, a pulse energy of 310 mJ, a pulse duration of 70 ps, and a beam quality factor M2 of <= 2 at a repetition rate of 100 Hz. The laser operates on a master oscillator power amplifier configuration, comprising the following: a neodymium-doped yttrium orthovanadate (Nd:YVO4) mode-locked oscillator, a laser diode-end-pumped neodymium-doped yttrium aluminum garnet (Nd:YAG) regenerative amplifier, a pre-amplifier, and a single-stage, dual-pass, traveling-wave amplifier. High-efficiency second-harmonic generation at 532 nm is achieved via type-I phase matching with a LiB3O5 (LBO) crystal. A green laser with 208 mJ pulse energy is generated using a 1064 nm laser with 310 mJ input, achieving a maximum conversion efficiency of 67.1%. The system emits cochannel laser pulses both at 1064 and 532 nm, representing a promising light source for spatial-target ranging.

A hundred-watt millijoule-level disk and single-crystal fiber cascade amplifier were demonstrated. We innovatively adopted a disk regeneration amplifier as the front end of the single-crystal fiber amplifier. After single-pass amplification by the single-crystal fiber amplifier, a hundred-watt millijoule picosecond laser output is obtained with an average power of 210.1 W and a pulse energy of 1.05 mJ. To the best of our knowledge, this is the first time that the single-crystal fiber amplifier has achieved both hundred-watt and millijoule simultaneously.

In this paper, we report on a cw-pumped cryogenically cooled Yb:CaF2 laser crystal regenerative amplifier that can produce >10.3 mJ, <285 fs laser pulses at 1034-nm and repetition rate of 1-kHz. We achieve record high optical pump to optical amplified compressed output efficiency at >14%. Using a symmetric cavity design to compensate thermal lensing effect, we were able to achieve excellent beam quality with measured M2 at 1.19 and 1.16 at horizontal and vertical directions, respectively.

We report on a continuous-wave (CW) pumped cryogenically cooled rod Yb:YAG regenerative amplifier delivering uncompressed 12-mJ, 90-ps, 1030-nm pulses at a 1-kHz repetition rate. The amplifier demonstrates an efficiency of 31.7%. A symmetric cavity design was utilized to compensate for the substantial thermal lensing effect, yielding a final measured beam quality of 1.1 in both horizontal and vertical directions. After significant gain narrowing, the measured spectra exhibit a bandwidth of 0.3 nm corresponding to an approximately 5 ps transform-limited pulse.

Hundreds of picosecond pulses amplifier based on Yb-doped tapered fiber can serve as the primary power amplifier stage for an all -fiber and polarization-maintained picosecond pulse laser system. Here, we report a high-power narrow-linewidth amplifier stage by using the Yb-doped tapered fiber. In the regime, we have demonstrated amplification of 201.4 ps pulses centered at 1031.4 nm with a spectral width of 0.54 nm to 105 W average power at a repetition rate of 29.3 MHz. The picosecond pulses had a high beam quality with a measured M2 value of 1.36 similar to 1.51, and the optical-to-optical conversion efficiency reached 56 %. To the best of our knowledge, this is the first demonstration of a high-power amplifier based on Yb-doped tapered fiber, capable of amplifying hundreds of picosecond pulses beyond the hectowatt-level average power, while maintaining high beam quality. This achievement highlights the immense potential of Yb-doped tapered fiber in the field of picosecond pulse power amplification. At last, we have refined the model for the transmission and amplification of picosecond pulses in Yb-doped tapered optical fibers, thereby enhancing simulation accuracy by 8 % and providing valuable references for the in-depth research of tapered fiber pulse amplifiers.

This paper introduces a compact picosecond laser system using tapered double cladding fiber-single crystal fiber hybrid amplification technology for the first time. By modifying the Ginzburg-Landau equation, we established a simulation model and designed a passive mode-locked picosecond oscillator based on a semiconductor saturable absorber mirror. The oscillator outputs laser with a pulse width of 7.75 ps, a center wavelength of 1030.55 nm, and a spectrum width of 0.58 nm. The seed laser is stretched and amplified by the all-fiber front stage, and then injected into the tapered double cladding fiber-single crystal fiber hybrid amplifier. The laser power is amplified from 820 mw to 103.1 W, obtaining a gain of 21 dB. We used zero-phonon line pumping technology in single crystal fiber amplifier to reduce the thermal effects caused by quantum loss, thereby increasing the length of the crystal and increasing the power loading capacity. We designed a single crystal fiber amplification module using Yb:YAG with 60 mm long, 1 mm diameter and a 1 at.% doping rate for the first time. Finally, a hundred-watt level picosecond laser output with a repetition frequency of 26.33 MHz, an average power of 103.1 W, a pulse width of 244.72 ps, a spectrum width of 1.16 nm, and a beam quality of M2 x = 1.368 and M2 y = 1.511 was obtained. To the best of our knowledge, this is the highest picosecond laser output power for an all-fiber front-stage combined with a single-stage single crystal fiber amplifier.

This paper introduces a CPA-free Yb:YAG thin-disk regenerative amplifier laser system. The seed pulse is generated by a passive mode-locked picosecond oscillator based on a semiconductor saturable absorber mirror, with a center wavelength of 1030.7 nm, a pulse width of 7.7 ps, and a repetition frequency of 26.3 MHz. After stretched and pre-amplified by an all-fiber front stage, the seed with a pulse width of 201.3 ps and a pulse energy of 15.2 nJ was obtained, then injected into the thin-disk regenerative amplifier. Yb:YAG crystal was chosen as the material for the thin-disk, with 100 mu m thickness, 9 mm diameter and 7 at.% doping rate. In order to increase the one-way round-trip gain of the thin-disk regenerative amplifier, a symmetrical dual-pass resonant cavity was designed to double the number of passing through the crystal on a round trip in the regenerative resonant cavity to reduce the times of cycles, intra-cavity loss and improve optical efficiency. We used a 969 nm fiber-coupled semiconductor laser as the pump source to pump the Yb:YAG thin-disk crystal. With zero-phonon line pumping technology, the quantum loss and thermal effect were reduced. In the end, we obtained a regenerative amplification output with an average power of 104.5 W, a repetition frequency of 200 kHz, a pulse width of 143.9 ps, and a spectrum width of 0.39 nm. The amplified pulse had quite good beam quality with Mx 2 = 1.09 and My2 = 1.14.

Picosecond pulse laser is the main light source for satellite laser ranging. In this paper, a 10 kHz repetition rate picosecond green laser with an average output power of 5.3 W is demonstrated. The laser generates a pulse width of 18.6 ps at a center wavelength of 532.20 nm with a spectral width of .066 nm. The beam quality is well preserved with M 2 of 1.1 with the beam divergence measured to be .62 mrad and pointing stability of 7 μrad over 30 min of operation. The laser system was then applied to measure the BeiDou satellite (Compass-I3) and generated a single range accuracy of 3.2 mm, which is the highest reported range accuracy for synchronous orbit satellite laser ranging.

To meet the needs of high-power fiber lasers, a new fiber structure called chirally coupled core (CCC) fiber has attracted the attention of researchers all over the world. CCC fiber consists of two cores, one of which is a central core distributed along the axial direction, and the other is a side core that is offset from the central axis and spirally distributed around the central core. Meanwhile, CCC fibers are helical-translation symmetric. The unique structure results in advantages of robust single-mode performance, mode-distortion-free splicing and compact coiling of CCC fiber. Based on a brief description of the theory about CCC fiber, this article focuses on the research progress and application prospect of CCC fiber.

High-power solid-state lasers are among the hot research directions at the forefront of laser research and have major applications in industrial processing, laser-confined nuclear fusion, and high-energy particle sources. In this paper, the properties of Yb:YAG and Nd:YAG crystals as gain media for high-power solid-state lasers were briefly compared, according to the results of which Yb:YAG crystals are more suitable for high-power applications. Then, the effects of the thermodynamic and spectral properties of Yb:YAG crystals with temperature were analyzed in detail, and it was shown that the laser beams amplified by the cryogenically cooled Yb:YAG crystals could have higher beam quality, higher pump absorption efficiency, lower pump threshold, and higher gain. The change in properties of Yb:YAG crystal at low temperature makes it more suitable as a gain medium for high-power lasers. Subsequently, two types of kilowatt-class lasers using cryogenically cooled Yb:YAG crystals as gain media are introduced—100 J, 10 Hz nanosecond lasers and 1 J, 1 kHz picosecond lasers. Their configuration, main parameters, and typical output results were analyzed. Finally, future directions in the development of cryogenically cooled Yb:YAG lasers are discussed.

利用SESAM光纤锁模激光器作为种子源,设计了行波放大器,对皮秒脉冲的放大特性进行了研究.利用中心波长为885 nm的光纤耦合半导体激光器直接泵浦Nd:YVO4晶体,有效降低了晶体中的热效应.通过两级行波放大,在泵浦功率为222 W时,获得了平均功率为33.7 W,重复频率为70.4 MHz,脉冲宽度为9.4 ps的脉冲输出.输出激光光束具有较好的圆度,光束质量因子M2在x方向上为1.15,y方向上为1.13.在8 h的连续运转下,激光器功率抖动性RMS<1％.

We demonstrate a high-power Nd: YVO 4 picosecond laser amplifier that is capable of generating 51.5 W of average output power at a wavelength of 1,064 nm, with a repetition rate of 70 MHz and a pulse duration of 8.5 ps. This system encompasses three stages of laser diode end-pumped Nd: YVO 4 amplification including two double-pass amplifiers and a single-pass amplifier. Laser output with near-diffraction-limited beam quality ( M 2 < 1.1) was maintained throughout the entire power scaling range of the laser. The system exhibited very high output power stability with a root-mean-square amplitude fluctuation of less than 0.2% over a period of 15 h of continuous operation.

Picosecond lasers with high average power and high beam quality have been widely used for precision processing and space exploration. In this study, we report a high-power picosecond green laser using a multistage Yb-doped rod-shaped photonic crystal fiber as an amplifier combined with a beam combination. The single amplification module achieves a 1,030 nm laser output of 146.8 W, and the maximum second harmonic generation (SHG) power is 92 W with a frequency conversion efficiency of 63.5%. The combined beam of the two SHGs resulted in a final output of 178 W with a repetition frequency of 24.07 MHz, pulse width of 50.1 ps, and beam quality factor of M 2 = 1.16. Furthermore, an adaptive filter control method of a two-axis fast-steering mirror was applied to suppress the beam jitter to up to 45 Hz.

Lasers with emission wavelengths of 1.5 μm are suitable for the eye-safe band and transparency region of the atmosphere. During extremely bad weather conditions, the penetration is stronger than the traditional 1 μm and visible band; thus, they are extensively employed in remote sensing, ranging, and imaging. In recent years, Er:Yb:glass has been widely used for generating 1.5 μm lasing, particularly for the generation of passively Q-switched pulses. Herein, different types of saturable absorbers (SAs) for Er:Yb:glass Q-switching have been reviewed, and the development of passively Q-switched Er:Yb:glass lasers based on these SAs has been discussed.