激光二极管抽运Nd:YAG双薄片激光器

Laser Diode-Pumped Nd∶YAG Double-Disk Laser

激光介质的热效应是高平均功率固体激光器面临的最大挑战,采用薄片激光介质是解决热效应的有效手段之一。当在抽运区尺寸远大于薄片厚度并且抽运光均匀分布的条件下,热流近似为沿厚度方向的一维分布,从而大大降低介质的热透镜效应和热致应力双折射。设计了四通光学耦合系统,通过提高二极管激光器阵列输出激光强度分布的均匀性,并优化经微柱透镜准直后光束的发散角,实现了抽运光的近平顶分布。采用两片1 mm厚的Nd∶YAG薄片激光介质,在两个峰值功率2000 W,占空比为15%的二极管激光器阵列抽运下,获得了峰值功率1440 W,平均功率216 W的准连续激光输出,光光转换效率达到36%,电光转换效率超过16%,在稳腔下测得的光束质量M2 因子约为12×13。

The key challenge for developing high-average power solid-state lasers is thermomechanical distortions caused by waste heat deposited in the gain medium by optical pumping. If a thin laser crystal disk is used with a nearly flat-top pump profile, the heat flux can be considered to be one dimensional. Thermal lensing and stress-induced birefringence are dramatically reduced. A nearly flat top pump profile is achieved with a good design for the four-pass optical coupling system. An average output power of 216 W is obtained from two disks with a thickness of 1 mm. The peak power of each diode array is 2000 W with 15% duty cycle. The optical-to-optical conversion efficiency of the laser system is about 36% and the electrical-to-optical conversion efficiency is more than 16%. The beam quality factor is measured to be 12 × 13 in a stable resonator.