为了实现固体激光器高功率、高光束质量的输出,设计了一种激光二极管(LD)阵列抽运的主振荡级与功率放大器(MOPA)结构的Nd∶YVO4激光器。该激光器的振荡级采用平-平谐振腔结构,并使用棱镜组对激光二极管阵列的抽运光整形,消除了激光二极管阵列抽运光不对称对振荡器输出光束质量的影响,在连续工作条件下获得了6.1 W的激光输出,其光束质量M2因子为M2x=1.14,M2y=1.13,光-光转换效率为25.6%。放大级采用具有近共焦、非稳腔特点的折叠光路结构,使振荡级激光光束10次通过放大级晶体,并且有效地抑制了放大自发辐射(ASE)和寄生振荡。在振荡级以6.1 W注入放大器时,得到最大输出功率26.8 W,此时放大器提取效率为29.1%,输出光束质量M2因子为M2x=2.08,M2y=1.92。

A Nd∶YVO4 laser in master oscillator and power amplifier (MOPA) structure pumped by laser diode (LD) stack is designed for the purpose of acquiring laser output with high average power and high beam quality from solid state lasers. The oscillator has a plane-pararellel resonator, and a prism group is adopted to reshape the pump beam from LD stack, which eliminates the impact on beam quality of oscillator by the asymmetry of the original pump beam. An average power of 6.1 W is achieved for continuous wave (CW) output, with near diffraction limit beam quality of M2 factor as 1.14 and 1.13 at x, y direction respectively, and optical-optical efficiency of 25.6%. In the amplifier, a near-confocal, unstable, multipass structure is used, in order to make the laser beam from the oscillator go through the Nd∶YVO4 10 times, and suppress the amplified spontaneuous emission (ASE) and parasitic oscillation as well. An output of 26.8 W, with an extraction efficiency of 29.1% is obtained while the oscillator provides the amplifier with a 6.1 W input. Meanwhile, the M2 factor of beam quality is measured to be 2.08 at x direction and 1.92 at y direction.