基于掺钕介质的热致频差可调谐同步双频脉冲激光器研究

Dual-frequency lasers (DFLs) with the frequency separations at 0-10 THz play important roles in many fields such as microwave， millimeter/terahertz wave signals generation and Doppler lidars. Currently, the researches mainly focus on the frequency separation tunability and the pulses synchronization functions of the DFLs. However, so far no further progress engaging the both functions in one DFL has been reported. Here, we propose a synchronized pulsed DFL with thermally tunable frequency separation based on the Nd-doped laser media. The Y-shape DFL cavity is established with two Nd-doped laser media with different parameters. The frequency separation tunability is achieved by the thermal-induced emission cross section (ECS) spectra shift of the two Nd-doped media; and the pulses synchronization is realized by a Cr4+: YAG passive Q-switch. The key points of the proposal are to discover the principle of the thermal-induced ECS spectra evolution of the Nd-doped media, particularly the central wavelengths shift and the peak values change of the ECS spectra; and construct a DFL experimental setup to generate the synchronized DFL pulses with tunable frequency separations. Comparing with the traditional ones, the tunable synchronized pulsed DFL makes itself a great innovation in the field of DFL theory and technology, which presents broad application prospect.

频差在0-10 THz的双频激光信号在很多领域有潜在的应用，如光生微波/毫米波、多普勒激光雷达和光生太赫兹波等。频差调谐和同步脉冲输出是双频激光器的两项重要功能，目前尚未有综合两项功能的双频激光器的报道。本申请提出了一种新思路，构建结合频差调谐和同步脉冲输出两项功能的可调谐双频脉冲激光器。具体思路是采用两种不同参数的掺钕介质构建Y 型双频激光腔，通过对掺钕介质热致发射谱漂移达成双频激光的频差调谐；利用双频激光共享一块被动调Q晶体实现双频脉冲的时间同步。重点研究掺钕介质发射谱随温度变化的本质，总结发射峰中心波长和发射峰截面值随温度的变化规律；设计搭建实验装置，实现时间同步的可调谐双频脉冲序列输出。较之传统的双频激光器，可调谐双频脉冲激光器融合了频差调谐和同步脉冲输出两项功能，是双频激光理论和技术领域的创新，具有良好的应用前景。

频差在0-10 THz的双频激光信号在很多领域有潜在的应用，如光生微波/毫米波、多普勒激光雷达和光生太赫兹波等。目前，尚未有综合频差调谐和同步脉冲输出两项功能的双频激光器的报道。本项目提出了一种新思路，构建结合频差调谐和同步脉冲输出两项功能的可调谐双频脉冲激光器。具体思路是采用两种不同参数的掺钕介质构建直现腔和Y型腔双频激光腔，通过对掺钕介质热致发射谱漂移达成双频激光的频差调谐；利用双频激光共享一块被动调Q晶体实现双频脉冲的时间同步。研究结果发现：基于Nd:YVO4/Nd:GdVO4组合增益介质的直线腔双波长CW激光器中，当抽运功率为3.0W时，改变增益介质的热沉温度从5.0°C改变为40.0°C，双波长激光器的频差从351.11减少至316.15 GHz。当增益介质的热沉温度保持在32.3°C时，获得了435mW功率平衡的双波长激光器信号，其频差为324.29GHz。在基于Nd:YVO4/Nd:YLF组合晶体的CW双波长激光器中，设置抽运功率为600mW，当热沉温度从7.0℃增加至22.0℃时，激光器获得了频差范围为4.58THz～4.63THz的双波长信号输出。当热沉温度处于17.8℃时，获得了功率均衡的，频差为4.58THz的双波长信号输出，此时输出功率为18.48mW。在基于Nd:GdVO4和Nd:YVO4 晶体的Y型腔双波长激光器中，通过独立调节激光器两晶体的热沉温度，控制热沉温度差从-50℃升高到 30℃时，获得了功率均衡状态下，频差调谐范围为266.05GHz～379.75GHz，输出功率为 230mW 的双波长激光信号。在基于Nd:YVO4/Nd:GdVO4组合晶体的可调脉冲双波长激光器中，采用脉宽调制的LD泵浦和Cr4 +:YAG晶体实现被动调Q，获得了波长为1063nm和1064nm的同步双波长激光脉冲信号。脉冲之间的时间抖动减少到脉冲时间宽度的约0.1倍。通过固定泵浦LD参数并将组合晶体的热沉温度从10°C调整到50°C，双波长激光信号的频差从344.11GHz降低到305.99GHz。在频差调谐的过程中，双波长激光器的脉冲相对峰值功率和时间同步保持相对稳定。较之传统的双频激光器，可调谐双频脉冲激光器融合了频差调谐和同步脉冲输出两项功能，是双频激光理论和技术领域的创新，具有良好的应用前景。