Hodgson N, Bostanjoglo G, Weber H
Appl Opt. 1993 Oct 20;32(30):5902-17. doi: 10.1364/AO.32.005902.
The properties of positive-branch and negative-branch unstable resonators with variable reflectivity mirrors and several variable internal lenses were investigated both theoretically and experimentally. Design rules for optimized unstable resonators for one or more active elements are derived on the basis of the ABCD matrix formalism. Experiments were performed with a pulsed Nd:YAG system consisting of three 6 in. × 3/8 in. (15.24 cm × 0.95 cm) rods. This system provided a maximum output power of 550 W per rod when a symmetric flat-flat resonator was used. Unstable resonators achieved up to 75% of this maximum value with beam-parameter products between 2 and 10 mm mrad. The beam quality becomes worse as more active elements are used inside the resonator. This deterioration of focusability is caused by spherical aberration in combination with differences of refractive power for r and Φ polarizations.
研究了具有可变反射率镜和多个可变内部透镜的正支和负支不稳定谐振器的特性，包括理论和实验研究。基于ABCD矩阵形式，推导了针对一个或多个有源元件的优化不稳定谐振器的设计规则。实验使用了由三根6英寸×3/8英寸（15.24厘米×0.95厘米）棒组成的脉冲Nd:YAG系统。当使用对称平-平谐振器时，该系统每根棒的最大输出功率为550瓦。不稳定谐振器在光束参数乘积介于2至10毫米毫弧度之间时，实现了高达该最大值的75%。随着谐振器内部使用的有源元件增多，光束质量会变差。这种聚焦能力的下降是由球差以及r和Φ偏振的屈光力差异共同导致的。
