An unstable resonator with seven large aperture ceramic disks and intra-cavity adaptive correction is presented.The composite ceramic disks with absorption rings were adopted to suppress amplified spontaneous emission.An intra-cavity aberration non-conjugate correction based on round-trip wavefront and relaxation iteration was applied in the resonator.After tilt and defocus were corrected in turn,an average output power of 4.5 kW was obtained.The corresponding beam quality factor β was 19.5.After tilt,defocus,and high order aberrations were corrected,the average output power was increased to 5.4 kW,and the beam quality factor β was improved to 6.8.

A high beam quality diode-pumped Nd:YAG master oscillator power-amplifier (MOPA) laser with three end-pumped slab amplifiers is developed. The Q-swtiched side-pumped rod oscillator presented a pulse energy 3.1 mJ with beam quality factors of M x2=1.17 and M y2=1.15 at a repetition of 1 kHz. The MOPA system delivered a pulse energy of 1.36 J with a pulse width of 48.2 ns and an extraction efficiency of 44.8%. The beam quality factors of M x2=1.72 and M y2=3.85 are measured without any phase-conjugators or adaptive optics.

为了验证近红外激光在水面大气传输时的热晕效应,采用缩比实验方法,克服了大口径和高功率系统复杂、实验成本高等实际问题,以理论分析为基础设计了高效的实验方案,对1000nm左右的激光水面大气传输热晕效应进行了实验研究,取得了重要的外场实验数据.结果表明,在选择合适的功率和发射口径情况下,1000nm左右的高能激光水面传输热晕效应可忽略.这一结果对大口径和高功率激光系统设计是有帮助的.

Aiming at the problem that the amplification of spontaneous emission (ASE) of high-power and large-diameter Nd:YAG slab amplifiers a simplified three-dimensional ASE calculation model is proposed based on geometric optical ray tracing method, which corrects the diffuse reflection of the fluorescence side and the calculation error introduced by the temperature effect of the stimulated emission cross section. Through numerical simulation, the contribution weight of fluorescence reflection of each surface of large-diameter slab (size 150.2 mm x 40.0 mm x 2.5 mm) to the ASE effect is determined, and the gain of small signal under different pump powers arc calculated. The effect of the ASE on the slab amplification performance is analyzed through the slab amplification. Experimental results and numerical calculations arc compared, and the validity of the calculation model is verified.

A YAG/Yb:YAG/YAG ceramic planar waveguide is manufactured using tape casting combined with vacuum sintering and hot isostatic pressing, which is taken as the laser gain medium to investigate the characteristics of laser amplification. A 1030 nm polarization-maintained (PM) fiber laser is used as the seed laser and a 910-nm diode laser array is used as the pumping source of the amplifier. The pumping light is coupled with the planar waveguide from the end facets. Subsequently, the amplification performances under front-end-pumping and back-end-pumping arc compared, and the amplification performances of dual-end pumping arc experimentally tested. In case of dual-end pumping, when the seed laser power is 136 W, the laser output power is observed to be 1.41 kW and the slope efficiency is up to 41%. To the best of our knowledge, this is the superior output power worldwide for a laser with this type of ceramic planar waveguide.

A quasi continuous wave Nd: YAG planar waveguide laser amplifier with a wavelength of 1319 nm is reported. The seed source is an oscillator based on a side-pumped rod Nd : YAG laser model, and the gain medium of the amplifier is a planar waveguide Nd: YAG. The size of the YAG planar waveguide is 0.6 mm x 10 mm x 60 mm, the central area 0.1 mm x 10 mm x 50 mm is the doped region, and the surrounding area is undoped YAG. The pump source of the amplifier is a diode laser array, which is coupled from the rear end into the planar waveguide gain medium. The seed laser is coupled into the gain medium via the end facet, and a single-pass amplification is introduced. In order to achieve the good heat dissipation, two micro channel heat sinks arc welded onto the Nd:YAG planar waveguide. The end facets arc coated high transmission at 1319, 1064 and 808 nrn. When the driving current of the diode laser arrays is 110 A and the pulse repetition rate is 200 Hz, the output of 36 nm 1319 nm laser is obtained, and the optical to optical efficiency is 8.3%.

We analyze the characteristic of amplified spontaneous emission (ASE) in a high power diode pumped Nd:YAG slab gain module. Simultaneously the characteristic of parasitic oscillation (PO) is considered. A high-efficiency three-dimensional coupled ASE calculation model using the geometric optical tracing technique is proposed. The model considers the stimulated emission cross-section correction by thermal effect and diffuse reflection on rough surfaces. From the experiment result of the fluorescence curve and small signal gain coefficient, the impact of ASE and PO on QCW-slab amplification is evident. Quantitative agreement between the ASE numerical model and experiment is achieved. The energy storage as well as the gain limit condition in QCW-slab amplification are investigated with the help of experiment. For the Nd:YAG slab with the size of 150.2 mm*30 mm*2.5 mm, the energy storage limit is 1100 mJ. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

The factors that influence the amplification efficiency of diode end-pumped Nd:YAG slab laser amplifier are theoretically analyzed, and a master oscillator power amplifier continuous wave laser system is designed. A narrow linewidth 1064 nm fiber laser is used as the seeder, and series and then double pass on two Nd:YAG slab laser amplifier is followed. The two Nd:YAG slab laser amplifiers have the same configuration, with the slab of 150.2 mm x 2. 5 mm x 30 mm, which are pumped in double end by diode laser array (DLA). The continuous laser is output when the amplifier is pumped at 21.6 kW, with output power of 5.4 kW, optical to optical efficiency of 24.8%, and beam quality beta of 3.5. Furthermore, the beam quality could be improved to 2.5 with the help of spatial filter.

The amplifier experiment research of end-pumped long pulse slab laser is developed, the results of out-put energy, optical-optical efficiency and pulse waveform are obtained at different experiment conditions, such as peak pumped power, amplifier power and pumped pulse width. The seed laser is CW fundamental transverse-mode operation fiber laser, the laser medium is composited Nd:YAG slab. Under end-pumped and the 2 passes, the laser obtain 7.65J out-put energy and 43.1% optical-optical efficiency with 45kW peak-pumped power and 386μs pump pulse width. The experimental results provide the basic for the optimization design to high frequency, high energy and high beam-quality slab lasers.

We demonstrate a master oscillator power amplifier (MOPA) architecture based on Yb:YAG amplifiers and adaptive optics (AO) systems with a high power and high beam quality laser output. With two conduction cooled, dual-end-pumped Yb:YAG zigzag-slab amplifiers at room temperature, the fiber laser of 300 W was scaled to 11.9 kW. Moreover, AO system positioned downstream was utilized to correct wavefront of amplified laser. The beam quality β at maximum output power was 2.8 times diffraction limited with closed-loop AO system.

We present investigations into a narrow-linewidth, quasi-continuous-wave pulsed all-solid-state amplified spontaneous emission (ASE) source by use of a novel multiple-pass zigzag slab amplifier. The SE fluorescence emitted from a Nd:YAG slab active medium acts as the seed and is amplified back and forth 8 times through the same slab. Thanks to the angular multiplexing nature of the zigzag slab, high-intensity 1064-nm ASE output can be produced without unwanted self-lasing in this configuration. Experimentally, the output energy, optical conversion efficiency, pulse dynamics, spectral property, and beam quality of the ASE source are studied when the Nd:YAG slab end-pumped by two high-brightness laser diode arrays. The maximum single pulse energy of 347 mJ is generated with an optical efficiency of ~5.9% and a beam quality of 3.5/17 in the thickness/width direction of the slab. As expected, smooth pulses without relaxing spikes and continuous spectra are achieved. Moreover, the spectral width of the ASE source narrows versus the pump energy, getting a 3-dB linewidth of as narrow as 20 pm (i.e. 5.3 GHz). Via the sum frequency generation, high-intensity, smooth-pulse, and narrow-linewidth ASE sources are preferred for solving the major problem of saturation of the mesospheric sodium atoms and can create a much brighter sodium guide star to meet the needs of adaptive imaging applications in astronomy.

A continuous-wave-operation laser amplifier chain consisting of three multi-concentration-doped Yb:YAG slab gain modules (GMs) at room temperature is presented. The output power of 22.3 kW with the beam quality of 3.3 times the diffraction limit is achieved from this chain. To the best of our knowledge, based on a Yb:YAG slab at room temperature, the highest power to date while maintaining excellent beam quality laser output. An extraction efficiency of 36% from the single slab GM is obtained and can be further enhanced to 46% by optimizing the parameters of GM. These results have confirmed that the Yb:YAG slab has an excellent scaling performance and is suitable for the development of high-average-power lasers.

In this Letter, we report a 1064 nm continuous wave Nd:YAG planar waveguide laser with an output power of 1544 W based on the structure of the master oscillator power amplification. A fiber laser is used as the master oscillator, and diode laser arrays are used as the pump source of the waveguide laser amplifier. The dimension of the waveguide is 1  mm (T)×10  mm (W)×60  mm (L), and the dual end oblique pumping is adopted with different angles. After a single-pass amplification, the power is scaled from 323 to 1544 W with the pump power of 2480 W, leading to an optical-to-optical efficiency of 49%. At the maximum output, the beam quality M2 are measured to be 2.8 and 7.0 in the guided direction and the unguided direction, respectively. To the best of our knowledge, this is the highest output power of a Nd:YAG planar waveguide laser to date.

A diode pump high power and high efficiency NdYAG planar waveguide oscillator at quasi-continuous mode is reported.The 1mm×10mm×60mm planer waveguide is selected as gain medium.The plane-plane cavity is built, and the output properties of the planar waveguide laser under different output mirror transmissions and different pulse repetition rates are studied.Experimental results show that when the output coupler transmission is 79％, an average output power of 441 Wfor the 1064nm laser is achieved under the pulse repetition rate of 500Hz and the drive current of 200A.Under five different repetition rates, the maximum single pulse energy is 928 mJ, and the effective optical to optical efficiency is 53.2％.The pulse waveform of output laser is consistent with that of the pump laser, and both have a pulse width of 240μs.The output power of the oscillator can be increased after the system optimization.

Taking Nd∶YAG planar waveguide as gain medium of a laser amplifier,we study the factors affecting optical-optical efficiency of laser with wavelength of 1064 nm during amplification.A free operational Nd∶ YAG rod oscillator with wavelength of 1064 nm is used as seed source,and a diode laser array with wavelength of 808 nm is used as the pump source.The pulse width of pump beam is equal to that of seed,and the output of pump beam and seed is synchronous.The size of the Nd∶ YAG planar waveguide is 60 mm× 10 mm× 1 mm,and the core thickness is 100 μm.The effects of seed energy,pump energy,and pump direction on the laser amplification efficiency are studied.The results show that when the input seed energy is 10 mJ,the quasi-continued laser with maximum energy of 713 mJ is obtained at the pulse repetition frequency of 100 Hz,the pump pulse energy is 1478 mJ,and the corresponding optical-optical efficiency is 47.6％.

We demonstrated a quasi-continuous wave (QCW) Nd:YAG planar waveguide laser amplifier with the single pulse output energy of 944 mJ. At the pulse repetition frequency (PRF) of 100 Hz, 1064 nm seed laser was coupled into the planar waveguide laser amplifier with the single pulse energy of 128 mJ and the pulse duration of 192 μs. With the total pump energy of 1582 mJ, the extracted energy of 816 mJ was obtained, leading to an optical to optical efficiency of 52% and an electrical to optical efficiency of 28%. To the best our knowledge, it is up to now the highest efficiency and output energy in Nd:YAG planar waveguide laser amplifier reported. At the maximum output, the beam quality factors M2 were measured to be 3.44 and 4.81 in the guided direction and unguided direction respectively, and the polarization degree was 98.6%. Higher average power could be obtained with the better performance of seeder oscillator.

A new Yb-doped silicate Yb3+ ∶ Sc2SiO5 (Yb∶SSO) has gained considerable attention in recent years because of its advantageous laser properties.Thermal lens focal length of Yb ∶ SSO in the case of different pump powers is calculated theoretically,and the influence of the material negative refractive index on the laser is analyzed.Quasi-continuous wave (QCW) lasing performance of the Yb ∶ SSO end-pumped by a 976 nm laser diode (LD) in a plane-plane cavity is studied.Laser output with peak power of 27.6 W and optical-to-optical conversion efficiency of 21.4％ is obtained when pump laser is with repetition rate of 50 Hz,pulse width of 500 μts and peak pump power of 128.8 W.Meanwhile,beam qualities factors (M2) in x and y directions are 1.24 and 1.20,respectively.Finally,the law of center-wavelength movement caused by the change of pump power is observed,and the cause of dualwavelength asynchronous oscillation is theoretically analyzed.

设计了一种高效率、结构紧凑的高功率激光放大器。采用解析方法分析了对称结构Nd:YAG双包层平面波导增益介质的内部热应力,获得了其可承受的最大抽运光强。针对不同厚度的内包层结构,采用Trace Pro软件模拟分析得到了最佳的抽运源结构和耦合系统。为了便于进行激光模式控制,掺杂区厚度取为100μm。内包层和外包层分别为纯YAG和蓝宝石,整个波导尺寸为60 mm×10 mm×2 mm。半导体激光器阵列输出的抽运光从波导的两个端面进入,两个大面和铜热沉焊接来获得良好的散热条件。种子光从一个端面注入,单通放大输出。通过模拟计算,在3384 W的抽运功率下,进入波导芯层的种子光功率为0.1 W,放大输出功率可以到达1322 W,光光效率约为39%。

利用端抽运板条放大器多角度通光的特点,建立了一套板条放大器各特性参数的测试系统,实现了动态加载条件下板条放大器的可提取功率、波前畸变及退偏度等多参数的同步测试。该系统包含千瓦级的窄线宽注入光源及提取功率测试系统,高精度热致波前畸变及退偏测试系统。当注入光源功率为2.7 k W,抽运电流为90 A时,板条放大器中可提取功率约为2.9 k W,波前畸变幅值差值小于1μm（27 mm口径）,热致退偏约为5.1%。对比无注入光时测得的放大器相关特性参数,两者差异较大,说明了该测试系统对于准确掌握板条放大器性能的必要性。

研究了一台端面抽运的Nd:YAG板条激光放大器,采用低掺杂、键合的Nd:YAG板条晶体和3通放大结构,实现功率330W,光束质量M2x=1.23,M2y=1.73的激光输出。采用4f像传递系统,有效减小了板条入口的切光损耗,并实现了板条内能量的均匀提取。根据1、3通放大功率计算了相应的增益系数,并简要分析了多通放大结构对放大自发辐射（ASE）的抑制作用。