【作者】 王强；

【导师】 鞠有伦；

【作者基本信息】 哈尔滨工业大学 ， 物理电子学， 2010， 硕士

【摘要】 2μm固体激光器作为发射机的相干多普勒测风雷达和差分吸收雷达成为近些年来激光雷达的研究重点。注入锁频2μm固体激光器,以其高能量、高光束质量、窄线宽、频率稳定的单频脉冲激光输出特性,成为激光雷达的首选光源。本文从理论和实验两个方面对注入锁频Tm,Ho:YAP固体激光器进行了研究。理论方面,首先根据Tm,Ho粒子的跃迁机制以及能量的传递过程,建立了低温下连续和调Q运转Tm,Ho双掺固体激光器的准四能级速率方程理论模型,得到激光跃迁初始反转粒子数密度的解析表达式,分析了各种参数对输出脉冲宽度的影响。其次根据注入锁频的经典理论模型分析了注入锁频理论,讨论了影响模式耦合的因素以及实现注入锁频所需的最小注入功率。实验方面,分析并设计了主、从激光器,通过注入锁频伺服系统控制,实现了Tm,Ho:YAP锁频激光输出。Tm,Ho:YAP主激光器采用微片结构,通过腔外加滤波片的方法,获得单纵模激光输出,讨论了激光器内多模振荡对输出功率和频率稳定性的影响,同时分析了输出激光光束质量较差的原因。从激光器采用四镜“8”字环形腔结构,通过对不同谐振腔长和输出镜透过率下激光器连续和调Q运行时输出特性的实验研究,选择了最佳的从激光器谐振腔参数。通过对注入耦合系统的设计,完成了种子光模式与环形腔模式的良好匹配,配合注入锁频伺服系统的控制,实现了Tm,Ho:YAP固体激光器的注入锁频激光输出,重频100Hz,单脉冲能量3mJ,脉冲宽度270ns。频率锁定时,激光脉冲建立时间缩短,单脉冲能量和脉宽的稳定性提高,通过拍频测量,验证从激光器输出为单频脉冲激光。最后,利用注入锁频Tm,Ho:YAP激光器,进行多普勒测速实验,实验处理结果与模拟目标的实际速度符合较好,为2μm波段激光光源在多普勒测风雷达方面的应用进行了初步探索研究。为了拓展国内注入锁频2μm固体激光器的工作物质范围,本论文对注入锁频Tm,Ho:YVO₄激光器进行了初步的实验研究,实现了Tm,Ho:YVO₄激光器的锁频激光输出,重频20Hz,单脉冲能量2mJ,脉冲宽度70ns。Tm,Ho:YVO₄晶体严重的热效应限制了其在获得高重复频率、高能量激光输出方面的应用,同时大的增益截面导致其输出脉冲宽度较窄,这些激光特性表明Tm,Ho:YVO₄晶体在作为多普勒测风雷达光源方面都不如Tm,Ho:YAP晶体。更多还原

【Abstract】 2μm solid-state lasers used as transmitter for Doppler wind lidar and Differential absorption lidar have become the research point of the lidar. Injection-locked 2μm solid-state lasers meet the requirements of light source for lidar due to their high energy, high beam quality, narrow linewidth, stable frequency and single frequency pulse laser output. In this paper, injection-locked Tm,Ho:YAP solid-state laser has been investigated theoretically and experimentally.Theoretically, firstly, based on level translation and energy transfer of Tm, Ho co-doped laser, the quasi-four-level rate equations of CW and Q-switch Tm,Ho laser operated in 77K are established. The analytical formula of initial upper level population inversion density is obtained. The mainly factors infect the output pulse width are discussed. Secondly, the theory of injection-locked is analyzed according to the classical theory model. The influence factors of mode coupling between the master laser and slave laser are analyzed. The minimum injected power which is essential to the injection-locked is discussed.Experimentally, injection-locked Tm,Ho:YAP laser is realized. The Tm,Ho:YAP master laser is a single-longitudinal-mode （SLM） operation laser by combining use the microchip structure and placing a ray filter outside the microchip laser. The influent factor of multi-mode oscillation in the cavity to the stability of output power and frequency are discussed. The reasons of the bad beam quality are also discussed. The slave laser is designed to be a ring laser, which is convenient for injection-seeded. Experimental studies on CW and Q-switched laser are carried out under different cavity length and output coupler. Then the optimum parameters of the cavity are selected. Good mode macthing between the master and slave laser is achieved by intensive designed. With the control of injection-locked servo system, the injection-locked Tm,Ho:YAP laser is obtained firstly. At repetition frequency of 100Hz, pulse energy of 3mJ and pulse width of 270ns is achieved. Under injected locking, the pulse buildup time shortened obviously. And the stability of output pulse energy and width is improved. The injection-locked laser is single frequency pulse laser verified by beat frequency measurement. Finally, a coherent laser Doppler velocity measurement experiment is carried out by using injection-locked Tm,Ho:YAP solid-state laser. The results of the experimental treatment are in good agreement with the actual speed, which means that it is possible to use injection-locked 2μm solid-state lasers to be as the light source of lidar at home.In order to expand the scope of laser materials applied to the injection-locked 2μm solid-state laser, injection-locked Tm,Ho:YVO₄ laser is realized. At repetition frequency of 20Hz, the pulse energy is 2mJ and pulse width is 70ns. Due to its serious thermal effects, it is difficult to achieve higher repetition rate and high pulse energy output of Tm,Ho:YVO₄ laser. And because of its large gain cross-section, the pulse width of Tm,Ho:YVO₄ laser is quite narrow. Therefore, compared with Tm,Ho:YVO₄ crystal, Tm, Ho:YAP is more suitable to be the laser medium as the light of lidar.更多还原