【摘要】 目前商用的半导体可饱和吸收镜(SESAM)产品可选择性低，每一批次指标一致性差，其物理参数与设计需求可能存在不可预知的差异，导致振荡器参数不可控，难以满足卫星激光测距(SLR)等对激光参数严苛的应用需求。文中通过使用分步傅里叶算法求解Ginzburg-Landau方程，建立仿真模型，提出SESAM参数需求，通过低压-金属有机化合物气相沉积方法将其制备出来，测试其参数为调制深度11.5%、非饱和损耗7.6%、饱和通量39.3μJ/cm~2、恢复时间5.5 ps、损伤阈值21.8 mJ。使用此SESAM搭建线型腔锁模振荡器，在注入泵浦功率为150 mW时，获得平均功率30.00 mW、重复频率44.57 MHz、峰值波长1064.07 nm、-3 dB光谱宽度0.14 nm、脉冲宽度31.50 ps的激光输出。该振荡器符合设计要求，并能通过调节腔长实现双峰、三峰、四峰锁模，应用于SLR系统将提高测距信噪比，获得更好的SLR精度。基于此模型进行大带宽啁啾光纤光栅作为输出耦合器的振荡器仿真时，结果失真，文中将啁啾光纤光栅带来的啁啾量引入Ginzburg-Landau方程，并建立方程描述光栅反射图谱。使用改进后的模型指导振荡器参数设计，经光纤预放大后获得平均功率55.70 mW、重复频率26.32 MHz、峰值波长1029.96 nm、-3 dB光谱宽度0.84 nm、脉冲宽度7.62 ps的皮秒激光输出。更多还原

【Abstract】 Objective Laser has good directionality,high brightness,good monochromaticity,and strong coherence making it significantly advantageous in the field of ranging.Satellite laser ranging (SLR) is the most accurate satellite ranging technology,and the kilohertz picosecond laser is the iconic light source of the fourth-generation satellite laser ranging.In kilohertz picosecond lasers,regenerative amplifiers are commonly used to amplify the mode-locked pulses,typically using Nd:YAG as the gain crystal with a gain bandwidth of 0.15 nm.In addition the smaller the bandwidth of the narrowband filter used for satellite ranging,the less the influence of ambient light,and the higher the signal-to-noise ratio.The narrowband filter bandwidth used by several observatories we cooperate with is 0.2 nm,so the laser spectrum width needs to be less than 0.2 nm.To match the gain bandwidth of the regenerative amplifier with the bandwidth of the narrowband filter,a requirement of an output spectrum width of 0.15 nm was proposed for the oscillator.Semiconductor saturable absorber mirrors (SESAM) have the advantages of stable performance,simple structure,low mode locking threshold,and the ability to achieve ful fiber integration.It has been widely used in mode-locked fiber lasers and has achieved product commercialization Most commercial applications of picosecond lasers are generated by SESAM passive mode locking technology SESAM products on the market have low selectivity and the consistency of each batch is poor.There may be unpredictable differences between the physical parameters of SESAM and the design requirements,resulting in uncontrollable oscillator parameters.Therefore,this study improved the passive mode locking model of SESAM to guide the design of oscillator parameters.Methods By using the Split-Step Fourier Transform (SSFT) to solve the Ginzburg-Landau equation,a simulation model is established,and SESAM parameter requirements are proposed.The simulation results mee the design requirements (Fig.1) and can achieve dual peak,triple peak,and quad peak mode locking by adjusting the cavity length (Fig.3).When using this model to simulate oscillators with large bandwidth chirped fiber Bragg gratings (CFBG) as output couplers,the results are distorted (Fig.9).The chirp dispersion brought by CFBG was introduced into the Ginzburg-Landau equation.Results and Discussions SESAM was prepared by low pressure metal organic compound vapor deposition (LP-MOCVD) method,and its parameters were tested as modulation depth 11.5%,non-saturated loss 7.6%,saturation fluence 39.3μJ/cm~2,relaxation time 5.5 ps,and damage threshold 21.8 mJ.The linear cavity oscillator achieves laser output with an average power of 30.00 mW,a repetition rate of 44.57 MHz,a peak wavelength of 1 064.07 nm a spectrum width of 0.14 nm and a pulse width of 31.50 ps when injected with a pump power of 150 mW (Fig.6)meeting the design requirements.It can also achieve dual peak,triple peak,and quadruple peak mode locking by adjusting the cavity length.The chirp dispersion brought by CFBG was introduced into the Ginzburg-Landau equation.The improved model was used to guide parameter design and obtain picosecond laser output with an average power of 55.70 mW,repetition rate of 26.32 MHz,peak wavelength of 1030.15 nm,spectrum width of0.58 nm,and pulse width of 7.62 ps after fiber pre-amplification.Conclusions In response to the SLR,we used the SSFT to solve the Ginzburg-Landau equation and established a simulation model and designed a set of SESAM parameters.The parameters of the linear cavity oscillator built on the basis of this SESAM meet the design requirements,and its application in SLR systems will improve the ranging signal-to-noise ratio and achieve better SLR accuracy.To solve the problem of the distortion in the simulation results of oscillators using large bandwidth CFBG as output couplers,the chirp dispersion brought by CFBG was introduced into the Ginzburg-Landau equation.An equation was established to describe the grating reflection spectrum.The improved model was used to guide parameter design,and the experimental results were consistent with the simulation results,verifying the rationality of the simulation model.更多还原