高功率激光二极管端面抽运复合晶体激光器的研究

Study of High Power Laser Diode End-Pumped Composite Crystal Lasers

在高功率激光二极管抽运固体激光器中,热效应已成为获得高输出功率和高光束质量的最大阻碍因素.用有限元方法研究了高功率激光二极管端面抽运Nd∶YVO4激光器中热透镜分布规律,提出了用复合晶体消除热透镜效应的方法.研究表明在端面抽运的传统单一Nd∶YVO4晶体激光器中,由于抽运功率密度很高,热透镜效应非常严重,由端面变形而造成的热透镜效应约占整个热透镜效应的50%;而采用复合晶体能够很好地消除由端面变形而造成的热透镜效应,同时得到很好的冷却效果,获得比采用传统单一晶体高出许多的基模输出功率和更好的光束质量.实验证明,采用复合结构晶体在23 W的抽运功率水平下得到了11 W的基模输出功率,光束质量因子M2 <1 5,光光转换效率达到48%.

Effect of thermal lensing is the main obstacle of getting high power and good beam quality in laser diode (LD)-pumped solid-state lasers. A theoretical investigation of effects of thermal lensing in an end-pumped Nd:YVO4 laser is demonstrated using finite-element-method, showing that the thermal lensing effect in high power LD-pumped Nd:YVO4 lasers is very serious, particularly the end deformation which accounts for 50% of the overall thermal lensing effect. The employment of a composite crystal has been demonstrated to be a useful method in relieving the thermal lensing, resulting in higher output power and better beam quality. The fundamental mode output power as high as 11 W has been achieved with 23 W pump power in composite crystal, the beam quality factor M2 is less than 1.5, and O-O conversion efficiency is up to 48%.