全固态调Q锁模光参量振荡中红外激光特性研究

The 3-5μm spectral region is in the range of most promising atmospheric transmission window. This spectral region has extensive applications. Optical parametric oscillator (OPO) can produce such laser. Recently, there is lots of research in continuously and Q-switched OPOs. Compared with the continuous wave mode locking, Q-switched mode locking leads to high peak energy and favors the high conversion efficiency and high peak energy OPO. Firstly, besides the four-mirror cavity, the inner cavity will be applied, which is often used in the Q-switched ns OPO. The length of the OPO cavity will be designed to prove synchronously pumping. The repetition rate of idler light will rely on the fundamental pulse. The designed SRO OPO will produce 3.3-4.8μm idler output in the project, which is pumped Q-switched mode-locking fundmental laser. The KTA crystal will be used as nonlinear media, which is put in a compound cavity or four-mirror cavity. The optical length of OPO and fundamental cavity will be matched to satisfy synchronously pumping. The repetition of mid-infrared idler light will depend on fundamental laser. The mechanism of the Q-switched mode-locking laser pumped OPO and the principle of the high conversion-efficiency and high peak-energy Q-switched mode locking OPO will be explored. The rule of the OPO and the optimization of the parameters will be studied. The work of the project will promote high-efficiency, high peak-energy 3-5μm Q-switched mode-locking laser and develop the application of the Q-switched mode-locking OPOs.

全固态3-5μm中红外波段激光，位于大气窗口，具有广泛的应用。光学参量振荡（OPO）是产生该波段激光的重要手段之一，调Q、连续波锁模OPO激光特性的研究较为广泛。与调Q、连续波锁模激光相比，调Q锁模激光具有更高的峰值功率，因此，调Q锁模激光泵浦的OPO有望获得更高的转换效率和更高的峰值功率。本项目拟利用调Q锁模激光作泵浦源，优良的KTA作为非线性晶体，采用复合内腔和四镜线型腔，设计OPO腔长与基频激光谐振腔长，实现同步泵浦并使中红外闲频光的重复率依赖于基频光，实现OPO的3.3-4.8μm闲频光单谐振输出。探索调Q锁模激光泵浦OPO产生中红外激光的机理，揭示高效率、高峰值功率3-5μm OPO调Q锁模激光产生的基本原理，研究OPO中红外调Q锁模激光的运转规律和输出参数的优化特性，为高效率、高峰值功率3-5μm调Q锁模激光的实现提供规律性依据，进一步拓展中红外锁模激光的应用。

位于大气传输窗口的3-5μm中红外波段激光在军事、民用等方面具有重要应用。以近红外作为基频光源，光学参量振荡器（OPO）能够实现此波段的闲频光输出。本项目研究了连续锁模、调Q锁模泵浦OPO的中红外输出特性。.在实验上，由于基频光性质对OPO的运转至关重要，首先对近红外调Q、锁模的固体激光器和光子光纤激光器的特性优化方面做了研究工作，对下一步研究的开展做了准备；其次，采用LD泵浦的、主动调制+被动锁模的钕离子激光器作为基频光源，技术成熟的KTA晶体作为非线性晶体，通过调节基频激光腔和OPO腔长度匹配，实现了调Q锁模泵浦的中红外OPO短脉冲输出。主动调Q开关有电光（EO）和声光（AO），饱和吸收体包括Cr:YAG和半导体饱和吸收镜（SESAM）。通过对实验数据的测量分析，得到了以下结论：一、调Q锁模泵浦的OPO具有更高的峰值功率；二、相比于外腔，内腔具有更高的基频光光子数密度，因此内腔OPO具有更高的转换效率。.在理论方面，探索了锁模激光泵浦OPO产生中红外激光的机理，将光强起伏机制引入动力学理论并首次给出了描述锁模泵浦的OPO的速率方程，电脑编程并得到了数值解，理论值与实验值契合较好。.项目在基频光源实验优化、OPO的腔型实验设计、动力学理论等方面对调Q锁模泵浦的OPO的输出特性做了研究，为高效率、高峰值功率3-5μm调Q锁模激光的实现提供了规律性依据，进一步拓展中红外锁模激光的应用。