N2O差分吸收激光雷达单频激光源频率控制技术研究

This project mainly investigates 1.9μm diode laser resonantly-pumped Ho:YAG single frequency, frequency-stabilization pulsed laser technology for the application of N2O Differential Absorption Lidar (DIAL). The mechanism to obtain 2122 nm single frequency laser output is theoretically studied. Meanwhile, parameters optimization of NPRO structure and experimental setup are carried out to achieve stable 2122nm single frequency laser output. Mathematical modeling is established to theoretically analyze internal and external factors which impact the frequency stability of single-frequency laser. N2O gas absorption cell frequency stabilization technology combined with PZT and temperature control method, is employed to ensure frequency stabilization. Time-domain modeling is established to analyze dynamics process of single-frequency injection locking. The factors affecting the success rate and frequency stability of injection locking pulse laser are analyzed, then dual PZT control technology, which combines the advantages of Ramp-Hold-Fire technique and Pound-Drever-Hall technique, is put forward to eliminate frequency jitter caused by internal and external factors. Polarization modulator is utilized to achieve fast switching between On-line laser and Off-line laser. Experimental setup is built up to validate theoretical models and frequency control technology to achieve laser wavelength and frequency stability requirements of N2O differential absorption lidar.

本项目针对N2O气体差分吸收激光雷达应用需求，开展1.9μm LD谐振泵浦Ho:YAG注入锁定单频激光器关键技术研究。对获得2122nm单频激光输出的机理问题开展理论研究，优化NPRO结构参数和实验装置，实现2122nm单频激光稳定输出；对影响单频激光频率稳定性的内外界因素进行理论分析和数学建模，采用N2O气体吸收池主动稳频技术结合PZT和温度双调谐手段，实现单频激光频率稳定。对单频注入锁定过程进行动力学时域建模分析，对影响注入锁定成功率及脉冲激光频率稳定性的因素进行分析，提出融合Ramp-Hold-Fire和Pound-Drever-Hall技术特点的双PZT控制的技术方案，消除内外因素对单频激光频率造成的抖动。采用偏振调制器实现On-line与Off-line种子激光的快速切换，搭建实验系统，对理论模型和频率控制技术进行实验验证，达到N2O差分吸收激光雷达对激光波长和频率稳定性的要求。

本项目针对N2O气体差分吸收激光雷达应用需求，重点对2122nm单频脉冲激光的实现方法开展了理论和实验研究。我们理论研究了Ho:YAG NPRO实现2122nm单频激光输出的运转机理，并优化了NPRO结构参数和实验参数，获得2122nm单频激光稳定输出。对影响单频激光频率稳定性的内、外界因素进行理论分析，采用融合Ramp-Hold-Fire和Pound-Drever-Hall技术特点的双PZT控制方案，提高单频脉冲激光的频率稳定性。获得脉冲能量5.9mJ、重复频率500Hz的单频脉冲激光输出，脉冲激光线宽1.43MHz，频率不稳定度1.26MHz。开发了Ho:YAG NPRO单频激光源原理样机，输出功率0.5W，线宽3.5kHz。.探索了Er:YAG 陶瓷NPRO单频激光器技术方案，采用1532nm光纤激光器作为泵浦源，获得10.7W单频激光输出，线宽5.75kHz。并开发了基于1532nmLD作为泵浦源的Er:YAG单频激光源原理样机，输出功率大于1W。.探索了基于石墨烯的被动调Q单频脉冲激光技术，在Ho:YAG扭转模腔内加入石墨烯材料，直接实现单频脉冲激光输出，并在腔内插入FP标准具，实现对输出波长的调谐，单频脉冲激光最大平均功率为149mW，脉冲重复频率为40.45kHz，脉冲宽度为3.45μs。.为了获得更大能量单频激光输出，研究了792nmLD泵浦Tm:YLF激光器技术，采用光纤耦合输出792nm LD单端和双端泵浦棒状Tm:YLF激光器，分别获得21W和31.7W激光输出，通过腔内插入的FP标准保证激光输出波长稳定在1908nm附近。同时，还研究了792nm叠阵半导体激光器端面泵浦Tm:YLF板条激光器，获得213W激光输出，无需在腔内插入额外光学器件，通过调制激光器输出透过率即可稳定输出1908nm激光。在实验研究基础上开发了单端泵浦Tm:YLF棒状激光器原理样机和双端泵浦Tm:YLF板条激光器原理样机。