高功率窄线宽中红外光参量技术研究

This project is to investigate an OPO and OPA technology to obtain high power and narrow linewidth Mid-IR lasers. The main task is to establish a theoretical model on hundred-Watt level Mid-IR lasers with 0.5 nm linewidth and 15% conversion efficiency. The corresponding experiments should also be carried out. In the theoretical model, we especially take into account the factors that are related to the spectral bandwidth in an OPO process. In an OPA process, thermal effects are especially important, which influence the conversion efficiency and the spectral bandwidth. The experiments should also be carried out to verify the theoretical model. A high power narrow linewidth Nd:YAG laser is used as the pump source. An optical parametrical MOPA scheme is used to obtain 3 μm Mid-IR laser output. In the OPO process, emphases are placed on the parameters of the intra-cavity components related to the spectral bandwidth. In the OPA process, we pay attention to the controlling of the temperature gradient of the nonlinear crystal. In this way, we can have high power and narrow linewidth Mid-IR laser output with high conversion efficiency.

项目研究一种获得高功率窄线宽的光参量振荡和放大技术，建立获得百瓦级3微米、光谱宽度小于0.5 nm、转换效率大于15% 的中红外激光输出理论模型，并进行相关的实验研究。通过理论模型的建立，重点研究OPO过程中引起光谱展宽的因素，OPA过程中的热效应对转换效率和输出光谱特性的影响。开展原理性实验研究，利用高功率窄线宽Nd:YAG激光作为泵浦光束，通过参量MOPA结构获得3微米中红外激光输出。通过OPO过程中对腔内光谱控制元件参数的合理选择，以及OPA过程中对非线性晶体温度梯度的控制，获得高功率窄线宽激光输出，提高非线性转换效率，验证并完善理论模型。

窄线宽3μm波段中红外激光在光电对抗、大气监测、太赫兹场产生等应用领域用途广泛，常采用光学参量振荡器（OPO）及光学参量振荡放大器（OPA）获得高功率窄线宽中红外激光，然而目前实现窄线宽百瓦量级的中红外输出还未见报道。项目的研究内容是研究一种获得高功率窄线宽的OPO和OPA技术，建立获得百瓦级3微米、光谱宽度小于0.5nm、转换效率大于15% 的中红外激光输出理论模型，并进行相关的原理实验研究。.通过项目研究，建立并完善了理论模型，编制了可视化仿真计算程序，对OPO和OPA中的参量过程进行了仿真计算，并根据计算结果开展相关实验研究。搭建了实验系统，获得了功率5.45W的2.9μm激光输出，信号光线宽0.3nm，系统转换效率为15.6%。项目研究中指出谐振腔不能有效限制横模进而导致的相位失配是引起高功率脉冲OPO线宽展宽的主要因素，同时分析了OPA系统中提高转换效率的方法，提出了功率百瓦级、光谱宽度小于0.5nm、转换效率大于15%的中红外OPO和OPA系统的设计方法和技术要点。