基于Ho掺杂钒酸盐晶体的谐振泵浦自调Q自拉曼中红外固体激光器

The 2.5μm mid-infrared solid state lasers have important applications in the fields of high precision spectral anslysis, photoelectric countermeasure, and nonlinear optical frequency conversion. At present, the researchers in the world have been widely attracted. Ho doped vanadate self-Raman lasers can generate 2.5μm laser. The project aims to deeply investigate the physical mechanism of self-Q-switching in Ho doped vanadate solid state lasers, to explore a convenient method of promoting intra-cavity peak power, and to realize the 2.5μm waveband self-Q-switched and self-Raman laser based on the Ho doped vanadate crystals. The main research contents as following: (1) The quasi-three-level rate equation theory model of the self-Q-switched Ho doped vanadate solid state lasers is established. The pulse output performances of the self-Q-switched Ho doped vanadate solid state lasers are systematically investigated, and the basic physical mechanism and necessary condition of self-Q-switching generation are revealed. (2) The influences of changeable parameters on the intra-cavity peak power of the 2μm laser are investigated, and the effective promoting method of intra-cavity peak power is obtained. (3) Considering self-Raman effect of Ho doped vanadate crystals, the dynamics of the self-Q-switched and self-Raman Ho doped vanadate solid state laser is investigated, the design scheme is optimized, and the high efficiency pulse laser output is realized in the 2.5μm waveband self-Q-switched and self-Raman Ho doped vanadate solid state lasers, for the first time. The project provides a new route for the generating of 2.5μm pulse laser.

2.5μm波段中红外固体激光器在高精度光谱分析、光电对抗、非线性光学频率变换等领域有重要的应用前景，目前已得到国内外极大关注。Ho掺杂钒酸盐自拉曼激光器可以产生2.5μm激光输出。本项目拟深入研究Ho掺杂钒酸盐固体激光器自调Q产生的物理机制，探索提高腔内峰值功率的方法，最终实现基于Ho掺杂钒酸盐晶体的自调Q自拉曼激光器。具体开展以下研究内容：(1)建立Ho掺杂钒酸盐自调Q固体激光器的速率方程理论模型，研究其自调Q脉冲激光的输出特性，揭示其自调Q产生的物理机制和必要条件；(2)详细研究各可变参数对腔内2μm激光峰值功率的影响，给出提升腔内激光峰值功率的有效方法；(3)在考虑Ho掺杂钒酸盐晶体自拉曼效应的基础上，开展基于该晶体的自调Q自拉曼激光器动力学的研究，优化设计方案，首次实现2.5μm波段Ho掺杂钒酸盐自调Q自拉曼激光器脉冲激光的高效输出。本项目为2.5μm脉冲激光的产生提供了新思路。

2.5μm波段中红外激光处于大气窗口，而且被称为分子指纹区，在诸多领域具有广阔的应用前景。在光电对抗中，2.5μm中红外激光器作为一种相干光源能够干扰、致盲甚至损坏敌方的人眼或传感器。2.5µm中红外波段还覆盖了HF和CH4等许多重要气体的吸收谱，因此可调谐2.5μm中红外激光光源在气体高精细光谱分析中有重要的应用。同时，2.5μm中红外激光器还是理想的非线性光学转换光源，用它泵浦ZnGeP2晶体可实现4~6μm的波长扩展。目前，有实力的国家都纷纷开展了相关晶体材料及激光器件的研究。本项目围绕1.94µm激光谐振泵浦Ho掺杂钒酸盐固体激光器的自调Q和自拉曼效应等关键问题开展研究，主要的研究工作总结如下：在详细分析了谐振泵浦Ho激光系统粒子跃迁过程和泵浦光传输特性的基础上，建立了Ho掺杂钒酸盐自调Q固体激光器的速率方程理论模型，理论研究了激光器自调Q脉冲激光的输出特性及动力学过程，探讨了基态能级对2μm波长光子重吸收效应以及激光器的可变参数对其输出特性的影响，阐明了Ho激光器自调Q产生的物理机制和实现条件，给出了提升腔内激光峰值功率的有效方法。在此基础上，结合Ho掺杂钒酸盐晶体拉曼转换效应，考虑激光场的三阶非线性受激拉曼散射效应，建立了自拉曼激光器运转的动力学理论模型，开展了基于该种晶体的自调Q自拉曼激光器动力学的研究，分析了基频光上能级粒子的自发辐射以及激光晶体自发拉曼散射效应对自调Q自拉曼激光输出特性的影响，给出了拉曼激光产生的阈值条件。选用a轴切割的掺Ho钒酸盐晶体作为2μm激光的增益介质和可饱和吸收体，实现2μm自调Q脉冲激光的高功率输出；在此基础上，基于钒酸盐晶体的拉曼频移效应，实现了2.5μm波段自调Q自拉曼脉冲激光的产生。