同轴-三平板型水介质脉冲输出开关实验研究

设计了用于脉冲功率装置的4 MV水介质同轴 三平板型输出开关。该脉冲功率装置将由24路相同的独立模块组成，每路模块由Marx发生器、中间储能器、激光触发气体开关、脉冲形成线、水介质脉冲输出开关、脉冲传输线等组成。水介质脉冲输出开关是同轴 三平板结构水介质多通道自击穿开关，由输入输出电极、预脉冲屏蔽板和连接部件组成。进行了有预脉冲屏蔽板结构和无预脉冲屏蔽板结构的自击穿水开关实验研究。有预脉冲屏蔽板结构开关的输入、输出电极都是半球电极，直径分别是8 cm和5 cm；无预脉冲屏蔽板结构开关为针 板结构，输入电极为平板电极，输出电极为直径3 cm的电极棒。Marx发生器充电70 kV，开关的击穿电压为3 MV，放电电流为450 kA。在3 MV等级的击穿电压下，有预脉冲屏蔽板结构开关的抖动约6 ns，没有预脉冲屏蔽板结构开关的抖动减小至3 ns。     

A narrow linewidth continuous wave Ho:YAP laser with a volume Bragg grating

We report a diode-pumped CW Ho:YAP laser at room temperature with a volume Bragg grating (VBG) instead of the conventional mirror. The Ho:YAP laser operated at 2117.9 nm, with output power 8.1 W. The optical-to-optical conversion efficiency is 51.9% and slope efficiency is 61.1%. Also, a stable output and a narrow line width less than 0.3 nm FWHM are achieved. This is the first time to report a Ho:YAP laser with a volume Bragg grating.     

Effects of the deformation of reflection volume Bragg gratings on the M-factor of super-Gaussian laser beams

When high-power laser beams pass through a volume Bragg grating (VBG), the surface of VBG occurs distortion because of thermal effects, and it results in the decline of the grating’s performance. Considering distortion of the surface induces differences of the index and period, the scalar wave equations for super-Gaussian (SG) laser beams propagating in the reflection VBG have been solved by using finite-different and sparse matrix methods. The changes of the total power reflection coefficient, the beam width, the far-field beam angle and the M²-factor for the laser beams through the reflection VBG with deformation have been analyzed quantitatively. It can be shown that the deformation of the VBG affects evidently on the intensity and phase distributions, the total power reflection coefficient, the beam width, the far-field divergence angle and the M²-factor. The beam width, the far-field divergence angle, and the M²-factor of the output beams increase significantly with the distortions of the grating. The influence of the distortions of the VBG on the power reflection coefficient, the far-field divergence angle and the M²-factor of the output beams are smaller for higher beam orders.     

Volume Bragg grating stabilized spectrally narrow Tm fiber laser

A Tm-doped large mode area (LMA) silica fiber laser has been locked to a stable wavelength of 2,053.9 nm using a volume Bragg grating (VBG). The measured spectral width of the laser output was <300 pm, limited by the spectrometer resolution. Although this laser had modest output (approximately 5W) and slope efficiency (41%), this new approach to spectrally limiting the output of LMA fiber lasers is inherently extendable to kilowatt powers, opening up several applications including high-power pulsed fiber lasers and spectral beam combining. Performance characteristics of the laser compared to one using a dielectric mirror as a high reflector are described, and the results imply low VBG losses.     

大功率780 nm半导体激光器的设计与制备

设计并制备了一款780 nm半导体激光器,并进行了外腔反馈锁模研究。利用金属有机化学气相沉积技术制备了激光器外延层,采用GaAsP/GaInP作为量子阱/波导层有源区,限制层采用低折射率AlGaInP材料。采用超高真空解理钝化技术,在激光器腔面蒸镀无定形ZnSe钝化层。未钝化器件在输出功率2.5 W时发生腔面灾变损伤（COD）,钝化后器件未发生COD现象,电流在10 A时输出功率10.1 W,电光转换效率54%。体布拉格光栅（VBG）外腔锁定前后,器件的光谱半峰全宽分别为2.6 nm和0.06 nm,VBG变温调控波长范围约230 pm。     

A High Conversion Efficiency Q-Switched Intracavity Nd:YVO_4/KTA Optical Parametric Oscillator under Direct Diode Pumping at 880nm

We report a high conversion efficiency Q-switched Nd:YVO_4/KTiOAsO_4(KTA) intracavity optical parametric oscillator(IOPO) operating near 3.5 um based on direct 880 nm laser diode(LD) pumping. A maximum average idler output power of 2.6 W with a pulse width of about 7.9 ns is achieved under an absorbed LD power of 45.4 W at a pulse repetition rate(PRR) of 10 kHz. The maximum optical-optical conversion efficiency from LD power to OPO mid-infrared(MIR) output of 6.74% is achieved. To our knowledge, this is the highest conversion efficiency for a KTA-IOPO by exploiting a Q-switched laser as the parent fundamental pump source. The beam quality factors M~2 of the MIR beam at the full output power with a PRR of 10 kHz are within 2.12 in both the horizontal and vertical directions, indicating a near Gaussian mode.     

260 W波长锁定光纤耦合输出泵浦模块实验研究

半导体光纤耦合输出泵浦源是光纤激光器的核心器件,其性能直接制约光纤激光器的输出水平。采用COS封装的高功率LD芯片,通过VBG外腔光谱锁定和精密光束整形变换技术,结合偏振合束与精密聚焦耦合技术将18个LD单元耦合进105 μm/NA0.22光纤,获得不低于260 W功率输出。实验表明,该模块在注入电流18 A时,可获得稳定输出连续功率264 W,对应电光效率52%,输出光谱中心波长975.92 nm,谱宽0.51 nm。该设计为获得高功率、高亮度波长稳定泵浦源提供了一条可行途径,光纤耦合输出模块工程化后可广泛应用在光纤激光器泵浦等领域。     

Efficient Cr:ZnSe laser with a volume Bragg grating

An efficient and narrow linewidth Cr:ZnSe laser pumped by Tm,Ho:GdVO₄ laser with a volume Bragg grating (VBG) is reported. The Cr:ZnSe laser operated at 2580 nm with emitting linewidth (FWHM) about 0.8 nm. Using the volume Bragg grating, 3.57 W of output was achieved under total incident pump power of 13.1 W, corresponding to optical-to-optical conversion efficiency of 27.3%. By use of conventional mirror, 4.11 W of output was achieved the same incident pump power and the optical-to-optical conversion efficiency is 31.4%.     

LD侧面泵浦电光调Q532nm脉冲激光器

 为了实现高可靠、窄脉宽、高峰值功率激光输出,采用侧面泵浦技术和电光调Q技术,设计出一种激光二极管侧面泵浦电光调Q全固态绿光激光器。采用结构简单、紧凑的平-平腔设计,其端镜和输出镜均为平面镜,获得较稳定的侧面泵浦Nd∶YAG腔外倍频KTP脉冲绿光激光输出。当泵浦电流为120A,重复频率为600Hz时,获得脉冲绿光的最高输出平均功率为3.62W,1064nm到532nm的转换效率为15.3%,其脉宽为21ns,峰值功率为300kW, 单脉冲能量为6.01mJ。实验结果表明：该激光器稳定性可靠,输出激光脉宽较窄、峰值功率高。     

Watt-level Pr^3+:YLF deep red laser pumped by a fiber-coupled blue LD module or a single-emitter blue LD

A power-scaled laser operation of Pr:YLi F4(YLF)crystal at 720.9 nm pumped by a 443.6 nm laser diode(LD)module was demonstrated.The 20 W module was used to pump the Pr:YLF crystal,and a maximum output power of 3.03 W with slope efficiency of 30.04%was obtained.In addition,a 5 W blue LD was also used to pump the Pr:YLF laser,and a maximum output power of 0.72 W was obtained at room temperature.The output power was limited by the wavelength mismatch between the single-emitter LD and the absorption peak of the crystal.     

Narrow Linewidth Tm:YLF Laser with Volume Bragg Grating Dual-End-Pumped by Equidirectional-Polarization Fiber-Coupled Laser Diode

We demonstrate a narrow linewidth Tm:YLF laser with a volume Bragg grating (VBG) that was pumped by an equidirectional-polarization fiber-coupled laser diode using a dual-end-pumping configuration. For an optimized output coupler with a radius of curvature of 150 mm and transmission of 15% at a wavelength of 1.91 μm, the maximum output power was 15.6 W for an absorbed pump power of 51.7 W at 1,907.93 nm, and the output had a narrow linewidth of 0.22 nm. This corresponds to an optical-to-optical conversion efficiency of 30.2% and the slope efficiency was 36.7%.     

Laser and self-Raman-laser oscillations of PBMoO4:Nd3+ crystal under laser diode pumping

Different regimes of laser operation and stimulated Raman scattering (SRS) for a laser diode (LD)-pumped PbMoO4:Nd3+ crystal have been investigated. Under 1.5 W LD pumping, the output power of the PbMoO4:Nd3+ laser in the free-running mode at 1056 nm reached 0.65 W with a slope efficiency of up to 53%. Using different LiF: F-2 saturable absorbers, we achieved a maximum pulse energy of 11 microJ at a 1.4 ns pulse duration and a maximum output power of 0.35 W (10 microJ) at a 7 ns pulse width in the passively Q-switched mode. PbMoO4:Nd3+ self-Raman-laser operation at 1163 nm (first Stokes) was obtained for the first time, to our knowledge. The self-Raman-laser output pulse energy was measured to be as high as 6 microJ and the pulse duration was estimated to be shorter than 500 ps.     

High power and efficiency of a 2044-nm c-cut Tm, Ho:YAlO3 laser

A high power and efficiency of c-cut Tm, Ho:YAlO₃ (YAP) laser is reported in the paper. The laser operated in continuous wave (CW) mode or Acousto-optical (AO) Q-switched mode at 2044 nm. The Tm, Ho:YAP crystal was cooled at the temperature of 77 K and pumped by a fiber-coupled laser diode (LD) with the centre output wavelength of 794.8 nm. In CW operation, a 9.30-W output power was obtained at a 150-mm physical cavity length, corresponding to a slope efficiency of 42.5%. In Q-switch mode, the output average power of 9 W was achieved at the pulse repetition frequency (PRF) of 10 kHz with a 130-ns pulse width. Moreover, the energy per pulse of 3.54 mJ in 47 ns was acquired at 2.5 kHz with a 75.3-kW peak power.     

脉冲LD泵浦电光调Q深紫外激光器

研制了千赫兹213 nm深紫外全固态激光器。激光器采用脉冲LD侧面泵浦方式和电光调Q技术,实现了10瓦级基频光的稳定输出。利用多次倍频技术,实现了稳定的213 nm深紫外激光输出。当LD泵浦电流为80 A时,213 nm激光输出的最大平均功率达到了151 m W,激光器重复频率为1 k Hz,激光脉冲宽度为10ns,功率不稳定度为3%。同时,对激光在非线性晶体中的偏振匹配和不同重复频率条件下的激光器运转特性进行了分析。     

50.2W high stability and high compact all-solid-state green laser with extra-cavity frequency-doubling at 500 Hz

A 50.2W high pulse energy green laser system at 532 nm was demonstrated by extra-cavity second-harmonic generation (SHG). The fundamental laser was based on laser diode (LD) side-pumped MOPA Q-switched technology, producing 79W of average power at the repetition rate of 500 Hz, while the pulse width was 6 ns. Type-II angle phasematched KTiOPO₄ (KTP) crystal was used as the nonlinear crystal. The 50.2W average power of 532 nm laser was obtained with the divergence angle less than 0.6 mrad and the corresponding peak power of 16.7MW. The optical frequency conversion efficiency from fundamental to green laser was up to 63.5%. The measured output power fluctuation was less than 0.38% in one hour operation.     

全固态激光中的光谱合成技术

对多种全固态激光中的光谱合成技术进行了探讨和研究，包括光纤激光、Yb:YAG板条激光和半导体激光。对于光纤激光，探讨了基于单个多层介质膜（MLD）光栅、一对MLD光栅、多个体布拉格光栅三种衍射光学元件的光谱合成技术中色散造成的光束质量退化问题，指出子束光谱线型的二阶矩全宽决定了光束质量的退化量，但所允许的光谱宽度又依赖于具体的技术选择途径。进而比较了三种光谱合成方案的优缺点。对于固体激光，实验演示了基于Yb:YAG晶体的板条激光实现光谱合成的原理可行性。通过设计一个基于MLD光栅的振荡器内的光谱合成装置，实现了7束子激光最高241 W的光谱合成输出，合成后光束质量β因子约4.1，表明大功率Yb:YAG板条激光具有通过光谱合束技术实现功率进一步提升的潜力。对于半导体激光，提出并设计了大模场外腔半导体激光+快轴光谱合成的技术。实验演示了9个1 mm宽LD芯片沿快轴方向的光谱合成，用β因子评价合成后的光束质量，在慢轴方向β≈6.3，在快轴方向β≈1.6，表明快轴光谱合成造成的光束质量退化是完全可控的。     

Propagation characteristics of annular laser beams passing through the reflection Bragg grating with deformation

When high-power annular laser beams produced by the unstable resonator pass through the volume Bragg grating (VBG), absorption of light in the VBG will induce a temperature increment, resulting in changes in surface distortion. Considering that the surface distortion of the grating induces index and period differences, the scalar wave equations for the annular laser beams propagating in the VBG have been solved numerically and iteratively using finite-difference and sparse matrix methods. The variation in intensity distributions, the total power reflection coefficient, and the power in the bucket (PIB) for the annular laser beams passing through the reflection VBG with deformation have been analyzed quantitatively. It can be shown that the surface distortion of the VBG and the beam orders of the annular beams affect evidently the intensity distributions, the power reflection coefficient, and the PIB of the output beam. The peak intensity decreases as the deformation of the VBG increases. The total power reflection efficiency decreases significantly with the increase in deformations of the VBG. The PIB of the output beam decreases as the obscuration ratio β and the deformation of the VBG increase. For the given obscuration ratio β, the influence of deformation of reflection VBG on the PIB of the annular beams is more sensitive with increase in distortion of the VBG and decrease in beam order.     

Narrow-band,tunable 2 μm optical parametric oscillator based on MgO:PPLN at degeneracy with a volume Bragg grating output coupler

A degenerate optical parametric oscillator (OPO) using an MgO:PPLN crystal and a volume Bragg grating (VBG) output coupler is presented. By changing the temperature of the VBG, the resonance of the OPO can be tuned exactly on the degeneracy point. A single-longitudinal and a multi-longitudinal mode pump scheme as well as the performance of the optical parametric oscillator on and off degeneracy are compared. It was found that the multi-longitudinal mode pump setup provides superior results with respect to spectral width and stability at degeneracy. At 2128.4 nm, a spectral width of less than 0.7 nm, an output power of 1.7 W with a slope efficiency of 31.8%, and low power fluctuation of 0.3% were achieved.     

KGW晶体外腔式高功率579nm喇曼黄光激光器

报道了579nm高功率KGd(WO4)2喇曼晶体外腔式喇曼黄光激光器的输出特性.基于808nm脉冲激光二极管侧面泵浦Nd∶YAG陶瓷、腔内BBO电光晶体同步延迟调Q和Ⅰ类临界相位匹配的LBO晶体腔外倍频方案,并通过外腔式KGW晶体Ng轴二阶斯托克斯喇曼频移,获得了579.54nm黄光激光输出.当脉冲信号重复频率为1kHz、532nm泵浦光最高平均功率为5.02W、脉冲宽度为10.1ns时,获得了最高平均功率2.58 W、脉冲宽度7.4ns、峰值功率348.6kW的579.54nm二阶斯托克斯喇曼黄光激光输出;532nm至579.54nm的光-光转化效率为51.4%、斜率效率为54.8%,光束质量因子Mx2-579.54=5.829、My2-579.54=6.336,输出功率不稳定性小于±2.35%.实验表明:外腔式喇曼结构能够高效地获得喇曼黄光,具有很高的光-光转化效率及良好的功率稳定性,并通过脉冲LD结合同步延迟电光调Q可获得高重复频率、高平均功率、窄脉冲宽度和高峰值功率的黄光激光输出.     

High-efficiency near-degenerate PPMgLN optical parametric oscillator with a volume Bragg grating

We demonstrate a high-efficiency near-degenerate periodically poled MgO:LiNbO(3) (PPMgLN) optical parametric oscillator (OPO) using a volume Bragg grating (VBG) output coupler (OC) pumped by a multilongitudinal Q-switched Nd:YVO(4) laser at 20 kHz repetition rate. A total parametric power of 4.3 W with a conversion efficiency of 60% is achieved in a double-pass pump configuration. The output power improvement over the case of a single-pass pump is nearly 60%. Both the signal and the idler bandwidths are less than 40 GHz and are confined within 170 GHz bandwidth at 2128.8 nm. Such efficiency is, to our knowledge, the highest ever achieved from a degenerate OPO using a VBG OC.