High power semiconductor laser array with single-mode emission

The semiconductor laser array with single-mode emission is presented in this paper.The 6-μm-wide ridge waveguides(RWGs)are fabricated to select the lateral mode.Thus the fundamental mode of laser array can be obtained by the RWGs.And the maximum output power of single-mode emission can reach 36 W at an injection current of 43 A,after that,a kink will appear.The slow axis(SA)far-field divergence angle of the unit is 13.65.The beam quality factor M;of the units determined by the second-order moment(SOM)method,is 1.2.This single-mode emission laser array can be used for laser processing.

高功率激光器光束质量测量的衰减缩束仿真研究

光束质量因子M^(2)是表征高功率激光器横模特性的主要参数,针对目前光束质量分析仪只能用于小口径、低功率激光器光束质量评估的问题,开展了高功率激光器光束质量测量的衰减缩束技术原理与仿真研究。建立了衰减缩束组件的仿真模型,利用有限元的方法对光学元件在高功率激光下的热致像差进行研究,得出热致像差的峰谷(PV)值小于82 nm时,对光束质量因子的影响小于5%。当光束通过衰减组件时,如果发生退偏,光束质量因子将偏小。基于泽尼克多项式和光束质量因子计算模型,研究分析了缩束组件波前畸变对测量的影响,并通过Zemax仿真分析看出,在装调时入射光与缩束组件中心光轴夹角视场小于7°时,对光束质量因子测量的影响小于5%。

Transverse mode instability mitigation in a high-power confined-doped fiber amplifier with good beam quality through seed laser control

In this work,a confined-doped fiber with the core/inner-cladding diameter of 40/250μm and a relative doping ratio of 0.75 is fabricated through a modified chemical vapor deposition method combined with the chelate gas deposition technique,and subsequently applied in a tandem-pumped fiber amplifier for high-power operation and transverse mode instability(TMI)mitigation.Notably,the impacts of the seed laser power and mode purity are preliminarily investigated through comparative experiments.It is found that the TMI threshold could be significantly affected by the seed laser mode purity.The possible mechanism behind this phenomenon is proposed and revealed through comprehensive comparative experiments and theoretical analysis.Finally,a maximum output power of 7.49 kW is obtained with the beam quality factor of approximately 1.83,which is the highest output power ever reported in a forward tandem-pumped confined-doped fiber amplifier.This work could provide a good reference and practical solution to improve the TMI threshold and realize high-power high-brightness fiber lasers.

Progress in particle-beam-driven inertial fusion research: Activities in Japan

Research activities in Japan relevant to particle beam inertial fusion are briefly reviewed.These activities can be ascended to the 1980s.During the past three decades,significant progress in particle beam fusion,pulsed power systems,accelerator schemes for intense beams,target physics,and high-energy-density physics research has been made by a number of research groups at universities and accelerator facilities in Japan.High-flux ions have been extracted from laser ablation plasmas.Controllability of the ion velocity distribution in the plasma by an axial magnetic and/or electric field has realized a stable high-flux low-emittance beam injector.Beam dynamics have been studied both theoretically and experimentally.The efforts have been concentrated on the beam behavior during the final compression stage of intense beam accelerators.A novel accelerator scheme based on a repetitive induction modulator has been proposed as a cost-effective particle-beam driver scheme.Beam-plasma interaction and pulse-powered plasma experiments have been investigated as relevant studies of particle beam inertial fusion.An irradiation method to mitigate the instability in imploding target has been proposed using oscillating heavy-ion beams.The new irradiation method has reopened the exploration of direct drive scheme of particle beam fusion.

Conceptual design of the Kumgang laser: a high-power coherent beam combination laser using SC-SBS-PCMs towards a Dream laser

In this review paper, we introduce a self-phase controlled stimulated Brillouin scattering phase conjugate mirror(SCSBS-PCM) and the Kumgang laser. The SC-SBS-PCM was proposed and demonstrated its success at the academic low power level, ~100 mJ@10 Hz. The Kumgang laser is under development to verify whether the SC-SBS-PCM is operable at the k W level. It is a 4 kW beam combination laser combining four 1 k W beams using the SC-SBS-PCM. If the Kumgang laser functions successfully, it will be the most important step towards a Dream laser, a hypothetical laser with unlimited power and a high repetition rate.

High power and beam quality continuous-wave Nd:Gd VO_4 laser in-band diode-pumped at 912 nm

We report on the performance of a continuous-wave Nd:Gd VO_4 laser in-band diode-pumped at 912 nm with high output power and excellent beam quality. The laser produced an output power of 19.8 W at 1063 nm with an optical efficiency of 59.3% and slope efficiency of 62.7%. The laser threshold was ~2.04 W of the absorbed pump power, and the laser output beam quality was ≤ 1.2 in the horizontal and vertical directions. The strength of thermal lensing at full output power(33.4 W of absorbed power) was measured to be an average of 8.6 diopters.It is shown that thermal lensing is reduced by a factor of 2 with respect to the Nd:YVO_4 lasers, thus opening a way for further output-power scaling.

High power generation of adaptive laser beams in a Nd：YVO4 MOPA system

We report efficient power scaling of the laser output with an adaptive bemn profile from an Nd：YAG dual-cavity master oscillator using a three-stage end-pumped Nd：YVO4 amplifier. We succeed ill the last switching of an excited laser mode by modulating an acousto-optic modulator loss in a dual-cavity master oscillator, thereby achieving temporal modulation of the output beam profile. The outputs from the master oscillator are amplified via a three-stage power amplifier yielding 36.6, 40.5, and 45.4 W of the maximum output at 116.8 W of incident pump power for the transverse electromagnetic, Laguerre-Gaussian, and quasi-top-hat beam, respectively. The prospects for further power scaling and applications via the dual-cavity master-oscillator power-amplifier （MOPA） system are considered.

ARCTURUS laser: a versatile high-contrast,high-power multi-beam laser system

With the latest configuration,the Ti:Sa laser system ARCTURUS(Düsseldorf University,Germany)operates with a double-chirped pulse amplification(CPA)architecture delivering pulses with an energy of 7 J before compression in each of the two high-power beams.By the implementation of a plasma mirror system,the intrinsic laser contrast is enhanced up to 10^-12 on a time scale of hundreds of picoseconds,before the main peak.The laser system has been used in various configurations for advanced experiments and different studies have been carried out employing the high-power laser beams as a single,high-intensity interaction beam(I≈1020 W/cm^2),in dual-and multi-beam configurations or in a pump–probe arrangement.

Two-dimensional beam shaping and homogenization of high power laser diode stack with rectangular waveguide

In this paper, the research work of twodimensional beam shaping and homogenization of high power laser diode (LD) stack by a rectangular waveguide is presented. Both the theoretical simulation and experiment results have shown that the diode stack beam can be shaped into a uniform square spot with a dimension of 10 mm×10 mm and the non-uniformity less than 5% along both directions of slow axis and fast axis, the shaped beam has a uniform pumping depth over 10 mm, which is well to be used for a rectangular laser medium end pumping.

一种大功率宽波段激光束散角的校准测试方法

在大功率激光系统的评价与分析中,激光器的光束品质是系统光束品质的决定性因素,也是激光器验收、鉴定的重要指标,其中束散角是判别激光光束质量的重要参数。本系统测试激光波长的范围比较宽,一般在0.532μm~10.6μm之间,没有合适的探测器能够覆盖整个波段,所以采用了一种新的方法来解决宽波段束散角的测量问题。选用CCD成像和扫描狭缝相结合的方法来实现宽波段激光光束束散角的测量,可见光和近红外波段(0.532μm~1.2μm)激光光束采用CCD法测量激光束散角,中红外波段(1.2μm~10.6μm)激光光束采用扫描狭缝法测量激光束散角。两种方法的结合可以较为精确地测量出不同波段的激光束散角。

用于高功率密度光束控制的光寻址光阀研制

为解决光寻址液晶光阀在高功率密度光束控制领域的应用限制,介绍一种可用于高功率密度激光系统的光寻址液晶光阀,该光阀开关比不低于140∶1,可在高于2300 W/cm^(2)的连续激光系统中正常工作。同时,所研制的光阀可在高重频吉瓦(GW)级功率密度的fs脉冲激光系统中正常工作,在该系统最大功率密度激光作用下,光阀未见明显温度变化,该脉冲激光系统最大平均功率密度超过300 W/cm^(2)。

万瓦级光纤激光双色镜合成技术

高功率光纤激光具有光束质量好、转换效率高、热管理方便和柔性传输等优势,在工业加工和国防领域具有广泛的应用需求.目前,受限于光纤中的非线性效应和模式不稳定效应,单链路光纤激光器输出功率的提升遇到了巨大挑战.为突破单链路激光功率限制,本文基于双色镜合成技术,利用两路自研近单模宽谱光纤激光放大器实现了10 kW近单模合束激光输出,合成效率约为98.3%,光束质量因子M^(2)约为1.29.为进一步提升功率,采用三路宽谱激光实现了13.52 kW合束激光输出,合成效率约为96.8%,光束质量因子M~2约为1.61.本文首次在实验上验证了双色镜合成技术的对宽谱激光的功率提升潜力和光束质量保持能力,通过增加合成路数以及提高单路激光功率,有望在保持高光束质量的情况下实现更高功率激光输出.

基于光纤合束器件的高功率全光纤相干合成技术研究进展与展望

介绍了目前研究中相干合成多采用空间结构的研究现状,分析了空间结构的相干合成方案需要复杂的光路调节且长时间工作稳定性欠缺,肯定了基于光纤合束器件的全光纤激光相干合成在相干合成光源中的稳定性与实用性,梳理了近年来基于光纤合束器件的全光纤激光相干合成方案,分别介绍了基于光纤耦合器、光子灯笼、相干信号合束器以及基于自成像效应实现全光纤合束的技术方案及研究现状,分析了不同光纤器件目前的主要限制因素和发展瓶颈,并展望了未来的发展方向。

基于小角度V形腔光谱合束的半导体激光器和频

通过小角度V形腔外腔光谱合束将两个808 nm半导体激光器合束,提高半导体激光器的输出功率及光束质量。两个合束单元分别工作在795.8 nm和800.5 nm,将所获光束通过非线性光学方法进行频率转换。外腔光谱合束实现输出功率为6.5 W快慢轴光束质量M^(2)=2.2×18.5的光束输出,所获光束慢轴M2因子相较于自由运转单管激光器提高了30%,外腔光谱合束效率为83%。基于所获光源,实现了半导体激光器小角度V形腔外腔光谱合束和频,获得输出功率为18.3 mW波长为401.0 nm的蓝光输出,和频效率为0.28%。

高功率激光器光束质量测量的衰减缩束实验

针对目前光束质量分析仪只能用于小口径、低功率激光器光束质量评估的问题,开展了高功率激光器光束质量测量的衰减缩束技术实验研究,搭建了缩束激光的波像差及光束质量测量装置,开展了缩束组件装调误差对光束质量影响的实验。实验结果表明,随着装调视场角度的增加,1/3倍缩束组件在1.2°视场处M^(2)测量偏差小于5%。搭建了偏振分光装置,研究了衰减组件对光束稳定性的影响。实验结果表明,随机偏振的准单模激光器的稳定性比多模激光更易受到衰减组件退偏的影响。搭建了高反式与楔板式高功率激光光束质量测量装置,对1 kW准单模激光进行光束质量测量。实验结果表明,在高反式测量装置中,待测光束通过高反镜时产生了退偏,从而导致光束质量测量结果偏小,楔板式测量装置的测量结果更能准确反映待测光的光束质量。

基于双色镜光谱合成9.6 kW合成光源

通过光纤激光光谱合成技术,可以打破单个光纤激光器输出功率受非线性因素制约的限制,实现更高功率的激光输出。通过梳理光谱合成技术的发展历程并分析其现状,对其原理及优劣势进行分析,结合自身研究,设计了一款便携式3路合成系统,通过设计及优化光纤激光器的放大结构,严格把控参与合束的子束光源的质量,将1055、1070和1085 nm三路高功率窄线宽光纤激光进行合束,对合成系统中采用的双色镜进行研究,对其膜系指标进行严格的设计,对高陡度截止滤光膜的设计方法以及制备工艺进行分析,对其热损伤规律及控制技术进行研究,优化整个合成系统,最终实现合成功率9650 W的高功率激光输出,合成效率92%,光束质量M2为1.7,并对未来双色镜光谱合成进行了展望。

液晶相控阵技术的研究进展

液晶相控阵是一种基于液晶的电控可编程光学相控器件,具有体积小、质量轻、功耗低和易于控制等优点。通过对入射光束相位的调制来精确控制波束转向,不仅实现了器件的空间快速灵活扫描,能够对运动中的目标进行自动跟踪、捕获和瞄准,而且使系统集成度更高,降低了制造成本,可广泛应用于激光雷达和空间光通信等领域。总结了国内外对液晶相控阵技术的研究进展,主要包括波束控制、系统分析建模和系统性能优化。同时也介绍了液晶相控阵在高能激光、空间光通信和激光雷达中的应用研究进展。

高功率高亮度半导体激光器合束进展

半导体激光器体积小、效率高,但单元输出功率低、光束质量差限制了其应用。介绍了提升半导体激光器功率及光束质量的最新进展,对各种技术途径和实验结果进行了综述报道,并具体介绍了中国科学院长春光学精密机械与物理研究所近年来在高亮度半导体激光器芯片及合束方面取得的进展。

大功率工业激光的功率密度分布及其应用

由于激光功率、光束的模结构与聚焦光斑形态等参数,对加工质量起着决定性作用,通过对工业加工用大功率激光束,特别是聚焦焦点的横截面功率密度分布的测量,可以了解不同激光器加工能力的差异,为激光加工质量的提高提供最基本的数据.采用大功率激光光束光斑质量诊断仪（LQD-1）,对几种工业加工用典型大功率激光的功率密度分布进行了测量,所测激光束的模式主要有准基模、混合模、多模,根据测量结果给出了其应用范围.

大功率半导体激光合束进展

经过近30年的发展,半导体激光器已由信息器件逐步发展成为能量器件,特别是大功率高光束质量半导体激光器,已从泵浦光源过渡成为直接作用光源,并部分应用在加工及国防领域。本文介绍了大功率半导体激光单元发展现状,分析讨论了各种激光合束技术及相应的合束光源,介绍了长春光机所在激光合束方面所做的部分工作,提出了我国半导体激光产业建设及发展的几点建议,并对半导体激光技术的发展新动向进行了展望。随着单元亮度的提升和合束技术的成熟,大功率半导体激光源作为间接光源和直接作用光源将在国防和工业领域大放异彩。