2.13微米脉冲单频激光器泵浦的窄线宽中红外ZGP-OPO研究

As a wide broadband tunable laser source, the Mid-Infrared Optical Parametric Oscillator (OPO) laser has widely applications in laser radar, spectroscopy, and gas detection. In some special application fields, such as, spectroscopy and gas detection, the Mid-Infrared OPO should possess not only high power, but also narrow-linewidth and a wide tuning range, which can improve the resolving ability of the system for spectrum and gas molecular. At present, the linewidth of OPO was narrowed by spectrum element or injection-seeded method which can not achieve the OPO in producing laser with high power, narrow-linewidth, and wide tuning, simultaneously. As a kind of frequency conversion devices, the conversion efficiency and linewidth of the parameter light of the OPO are directly influenced by the output performance of the pump. In this research, we propose to employ the 2.13 µm pulsed single frequency laser pump ZGP-OPO at the first time, which can narrow the linewidth of the ZGP-OPO parameter and thus fundamentally improve its spectral characteristic. To improve the output performance of the ZGP-OPO pumping source, we optimized the configuration and parameters of the 2.13 µm pulsed single frequency Ho:YAP laser. We optimized the design of the resonator configuration and the pump coupling system to achieve the OPO laser output with high efficiency, wide tuning, and narrow linewidth. We hope that the OPO pumped by 2.13 µm pulsed single frequency laser will be a high performance research tool in the spectroscopy and gas detection applications.

中波红外OPO作为一种宽频可调谐激光光源已被广泛应用于激光雷达、光谱学及毒气侦测等领域。在光谱学、毒气侦测等应用领域，中波红外OPO在具有较高功率的同时，还应具有较窄的线宽和一定的调谐范围，从而提高对光谱及毒气分子的分辨能力。目前获得窄线宽OPO常用的光谱元件窄化法和种子注入法无法使OPO同时具备高效率、窄线宽、宽调谐特性。而OPO作为一种频率转换器件，其泵浦光特性将直接影响OPO参量光效率、线宽等特性。本课题首次提出以2.13µm脉冲单频激光泵浦ZGP-OPO，压窄ZGP-OPO参量光线宽，从根本上改善ZGP-OPO参量光光谱特性。通过优化2.13µm脉冲单频Ho:YAP激光器结构及参数，提升ZGP-OPO窄线宽脉冲泵浦源整体性能；进而通过谐振腔结构、泵浦耦合系统等的优化设计实现ZGP-OPO高效率、宽调谐、窄线宽中波红外激光输出，以期为光谱学、毒气侦测等领域提供一种性能优良的研究工具。

中红外波段激光处于大气窗口进和人眼安全波段，在光电对抗、激光遥感、激光医疗和环境监测等方面有重要的应用价值。本课题针对激光雷达及光谱、分子检测等领域对窄线宽3-5μm激光的应用需求，开展了窄线宽ZGP-OPO的研究工作。首先，针对Tm:YAP 激光器高功率运转时热效应严重的问题，采用板条状Tm:YAP 晶体作为激光介质，缓解激光晶体热效应；利用双凹谐振器结构补偿Tm:YAP晶体热透镜效应；利用F-P标准具实现对Tm:YAP输出激光波长的控制。最终获得了最高功率接近70W的1.94µm激光输出，为Ho:YLF注入锁频激光器提供了激光泵浦源。之后，以Tm:YAP激光器为泵浦源，开展了Ho:YLF注入锁频激光器的研究工作。分别设计了双F-P标准具Tm,Ho:YLF连续单纵模主激光器和四镜8字环型腔Ho:YLF从激光器，实现了Tm,Ho:YLF主激光器2.05μm单纵模激光输出及Ho:YLF环型腔从激光器连续及调Q脉冲激光输出。在此基础上，设计注入锁频激光器注入耦合系统，并将Tm,Ho:YLF主激光器输出的2.05μm单纵模种子光注入到Ho:YLF四镜环型腔从激光器中，利用“ramp hold and fire”技术实现了Ho:YLF激光器的种子注入锁定。在100Hz重复频率条件下，获得了单脉冲能量4.3mJ、脉冲宽度58ns的2.05µm脉冲单频激光。最后，利用Ho:YLF注入锁频激光器可获得近傅立叶转换极限线宽2μm脉冲激光输出的特点，以2.05μm单掺Ho:YLF注入锁频激光器为泵浦源泵浦ZGP-OPO，采用压缩ZGP-OPO泵浦光线宽的方式实现了ZGP-OPO参量光线宽的压缩，获得了脉冲能量0.3mJ、线宽5nm的3.01μm中红外激光，从而为获得窄线宽中红外激光提供了一种新的技术途径。