We present an adaptive optics (AO) system for a 1.94-µm laser source. Our system consists of a home-made Shack-Hartmann wavefront sensor and silver-coated bimorph deformable mirror operating in a closed-loop control scheme. The wavefront sensor used an uncooled vapor phase deposition PbSe focal-plane array for the actual light sensing. An effect of thermal afterimage was found to be reducing the centroid detection precision significantly. The effect was analyzed in detail and finally has been dealt with by updating the background calibration. System stability was increased by reduction of control modes. The system functionality and stability were demonstrated by improved focal spot quality. By replacing some of the used optics, the range of the demonstrated mid-IR AOS could be extended to cover the spectral range of 1-5 µm. To the best of our knowledge, it is the first AO system built specifically for mid-IR laser wavefront correction.

Thin-disk lasers are present in science and industry since the early 90s, yet not so many companies offer them commercially. This was a strong motivation for HiLASE to develop a versatile thin-disk laser platform that would be easily customized to user’s needs and provide a wide range of laser parameters, like output power up to 100 W, pulse energy up to 20 mJ, repetition rate 1-200 kHz, 1 ps pulse duration and wavelength range from Mid-IR to UV. During this presentation, we would like to introduce several customized systems used in different applications and their successful integration into industrial processes.

The fluctuation-magnification effect on the peak intensity of a laser pulse caused by the nonlinear Kerr effect in the chirped volume Bragg grating (CVBG) compressor is investigated experimentally for a high-energy, thin-disk, chirped pulse amplification system. The nonlinear Kerr effect occurs at the blue end, and the accumulated nonlinear phase shift (B-integral) in the CVBG rises with the increase of laser pulse energy. Experiments show that small fluctuations in peak power of uncompressed pulses cause increasing of the temporal fluctuation and spatial fluctuation due to high Kerr-nonlinearity in the CVBG when B-integral is larger than pi. Thus the initial fluctuation would be magnified by the CVBG compressor. (C) 2022 Society of Photo-Optical Instrumentation Engineers (SPIE)

We reported a simple and compact Yb-doped fiber femtosecond oscillator, which is based on a dispersion management and nonlinear polarization evolution (NPE) technique. Here, 84 fs, 4 nJ at 1030 nm pulses were generated directly from the mode-locked fiber oscillator by optimization of the net dispersion of the cavity. Only a pair of gratings was used to compensate the positive dispersion caused by the fibers and other optics in the cavity. This is, to our knowledge, the shortest pulse duration directly from a fiber oscillator without any extra compressor outside the cavity.

HiLASE facility focuses on development of high average power pulsed lasers with picosecond and nanosecond laser pulses. Recently, lasers with 500 W average power with picosecond pulses and energy of 5 mJ and 1 kW average power with nanosecond pulses and energy of 100 J were reported. Current status and future plans of the HiLASE facility are presented.

In order to produce laser projectors in large quantities, a green laser with compact structure stable performance and low cost as the green light source was need. In this paper, a compact microchip laser array was obtained, utilizing optical-contact Nd:YVO4/PPMgOLN bar as gain media and frequency doubler, combined with soldering packaging technology. Three green beams of the laser were obtained with the total output power of 223.7 mW, each laser beam had good spot profile and stability, the microchip laser array had compact size of 47 mm×35 mm×25 mm. It had a fluctuation of less than ±2.5%for 2.5 h. Various performances of the laser would fully meet the requirements of laser projector as the green light source, and it could be mass-produced in low cost.

In this paper, a practical model of a thin disk regenerative amplifier has been developed based on an analytical approach, in which Drew A. Copeland [1] had evaluated the loss rate of the upper state laser level due to ASE and derived the analytical expression of the effective life-time of the upper-state laser level by taking the Lorentzian stimulated emission line-shape and total internal reflection into account. By adopting the analytical expression of effective life-time in the rate equations, we have developed a less numerically intensive model for predicting and analyzing the performance of a thin disk regenerative amplifier. Thanks to the model, optimized combination of various parameters can be obtained to avoid saturation, period-doubling bifurcation or first pulse suppression prior to experiments. The effective life-time due to ASE is also analyzed against various parameters. The simulated results fit well with experimental data. By fitting more experimental results with numerical model, we can improve the parameters of the model, such as reflective factor which is used to determine the weight of boundary reflection within the influence of ASE. This practical model will be used to explore the scaling limits imposed by ASE of the thin disk regenerative amplifier being developed in HiLASE Centre.

The development of kW-class diode-pumped picosecond laser sources emitting at various wavelengths started at the HiLASE Center four years ago. A 500-W Perla C thin-disk laser with a diffraction limited beam and repetition rate of 50–100 kHz, a frequency conversion to mid-infrared (mid-IR), and second to fifth harmonic frequencies was demonstrated. We present an updated review on the progress in the development of compact picosecond and femtosecond high average power radiation sources covering the ultraviolet (UV) to mid-IR spectral range at the HiLASE Center. We also report on thin-disk manufacturing by atomic diffusion bonding, which is a crucial technology for future high-power laser development.

研制出钒酸钇晶体与掺氧化镁(2％)的铌酸锂晶体(Nd∶YVO4/PPMgOLN)光胶合的小型列阵微片绿光激光器.在两点泵浦驱动下,激光二极管(LD)输入总功率为922 mW,腔内倍频下输出532 nm的单频绿光功率最高为200mW,光—光转换效率为21.7％.在相同条件下,与单点泵浦激光器进行对比分析,结果表明温度对铌酸锂晶体的倍频效率有很大的影响;由此,通过控制半导体制冷器(TEC),对激光器在两点泵浦驱动下不同温度时的转换效率进行测试,得出当铌酸锂晶体温度在27℃时达到最佳相位匹配.

Pulse width of 8.7 ps was broadened to 102.2, 198 ps with single and double pass the VBG respectively. When the 102.2 ps pulse was injected into 1 kHz repetition rate of LD side-pump Nd: YAG regenerative amplifier (RA), pulse width of 87.5 ps at 1 kHz was obtained with the pulse energy of 9.4 mJ, the beam quality of M^2 factor was 1.2. The pulse width was compressed to 32.7 ps with a single pass VBG and the pulse energy reduced to 8.8 mJ, and the power density was up to 15.2 GW/cm2, the stability for pulse to pulse rms is about 0.6 %, beam pointing was about 35 μrad. In addition, when 198 ps pulse was injected into RA, pulse width of 156 ps was obtained which energy was 9.6 mJ, the pulse width was compressed to 38 ps by double passing the VBG, the pulse energy decreased to 8.5 mJ. Chirped VBG is a new way to obtain high-intensity picosecond pulse laser system simple and smaller.

We report the generation of high-order Stokes and anti-Stokes picosecond laser light by using an YVO4 Raman seed-amplifier system. This system can eliminate filametation induced by nonlinear effect. The two key elements for the system are seed-pump time synchronization and the incident angle between Raman seed and pump, which are studied in details. The result proves that Raman seed-amplifier system is a simple and practical way to get multi-wavelength picosecond lasers.

Here we report that the properties of the poling electrode is one of the most important factors in fabrication of the ferroelectric crystal poling. In this paper, systematic researches on the property of electrode coating and the forms of electrode contact have been made. By using pulse applied electric field, the periodically poled grating of 31.2μm was prepared on a 1mm thick 5% MgO-doped Lithium Niobate crystal. A wavelength of 1064nm pulse laser was used as fundamental source to operate optical parametric oscillation experiment, and 1.141W of idler output power was obtained when PPMgOLN pumped by 1064nm of 5.567W at the temperature of 80℃. The maximum conversion efficiency from incident pump power to the idler output achieved to 20.1%.

Periodically poled crystals are widely used as SHG, DFG, SFG, OPO and THz generation, and there is a broad application prospect in some areas such as the laser display, optical fiber communication, atmospheric exploration and military confrontation. At present, to get the parameters of periodically poled crystals, like duty ratio, the main method is chemical etching of the samples. In this paper, we present a nondestructive characterization system of periodically poled crystals. When we apply a proper high voltage on both sides of the periodically poled crystal, the refractive index difference of positive and negative domain will be increased and we can observe a clear domain pattern by the a microscope so as to obtain general information. Then a single frequency laser is prepared to radiate on +z surface of the periodically poled crystal, we can get some orders of diffraction according to diffraction optics principle. Finally, we can measure the parameters such as period, duty ratio by use of numerical analysis. The testing sample size of this system can be up to 60mm, The accuracy of the testing period can be 0.1μm, and the measurement range of duty ratio is 20%-50%.

A high power Q-switched all solid state master oscillator power amplifier (MOPA) laser system is reported in this paper, which produces linearly polarized light 89 W at 500 Hz in 5.5 ns (FWHM). Bidirectional voltage supplied electro-optic Q-switched technology was used in oscillator stage, which obtained adjustable pulse width from 5.5 to 21 ns in 1064 nm. Through multistage Nd:YAG amplifiers at the pulse width of 5.5 ns, the oscillator laser power was scaled up to 89 W and the corresponding peak power reached 32.3 MW with power instability less than 0.51%.

We compare the stimulated Raman scattering (SRS) performance of a-cut and c-cut YVO4 in a single-pass Raman experiment. The undoped YVO4 crystal shows its good SRS capability in a quasi-transient field. The non-axial scattering angles of Raman radiation are also studied, and the result is in good agreement with the physical model based on the phase matching condition. High-order Raman Stokes and anti-Stokes lights with good beam quality are obtained by means of Raman amplification. Our experiments show that Raman amplification is a practical way to avoid unexpected nonlinear effects and to obtain new wavelength picosecond lasers.

The Raman property of undoped YVO4 is studied. The spontaneous Raman spectrums of a-cut and c-cut YVO4 are measured and compared, which show their great stimulated Raman scattering (SRS) capabilities. The energy thresholds with different pulse widths are measured in single pass Raman generator. The non-axial scattering angles of Raman Stokes light are calculated, and the experimental results get good agreements with the calculated value.

We present a high compact structure laser diode (LD) side-pumped all-solid-state Q-switched master oscillator power amplifier (MOPA) laser system with high beam quality. Bidirectional voltage-supplied Q-switched and MOPA technologies were introduced in the design. An in-center wavelength of 1064 nm with pulse width adjustability from 5 to 18 ns was obtained at the repetition rate of 500 Hz. Through multistage Nd:YAG amplifiers at the pulse width of 6 ns, the oscillator was scaled up to 145 W and the corresponding peak power reached 48.3 MW with single pulse energy fluctuation less than 0.45% in 1 h operation. (C) 2013 Society of Photo-Optical Instrumentation Engineers (SPIE) [DOI: 10.1117/1.OE.52.2.024202]

Abstract. A third-harmonic-generation picosecond pulse with several millijoules per pulse at 355 nm has been achieved by nonlinear optical materials LiB3O5 (LBO). The single pulse energy of third harmonic was up to 2 mJ at the repetition rate of 1 kHz. The conversion efficiency was up to 33.3% from 1064 to 355 nm with the M2 factor of 2.4. The system is based on a Nd:YAG regenerative amplifier with a simple double-pass post-amplifier.

We successfully presented a multi-pulse picosecond laser with passively mode-locking, grating-stretching, regenerative amplifier and grating compression technologies. Firstly, 8.5ps pulses with a repetition rate of 143MHz and a maximum average output power of 160mW were obtained by a semiconductor saturable absorption mirror (SESAM). Secondly, we got the pulses width stretched to 99.9ps with 90mW and single grating. Thirdly, a pulse sequence with each of five pulses per group was obtained by using a multi-pulse regeneration amplifier system, from which output energy was about 28mJ at the repetition rate of 1kHz and 112.1ps in single pulse width. Finally, using a grating compressor we acquired these pulses compressed to a pulse width of 28ps and 14mJ in each group at a repetition rate of 1kHz.