针对通过测量输出光椭圆度对环形激光器进行调腔的要求, 研究并建立了环形激光器双光路椭圆度测量系统。计算分析了无源环形腔对S线偏光和P线偏光的频率响应特性, 得出S线偏光谐振峰频率特性更适于无源环形腔的稳频。采用S线偏光作为外部输入光来提高稳频精度, 搭建了环形激光器双光路稳频与测量系统。环形激光器稳频系统在10 s内就能完成稳频, 稳频效率高, 稳频后光强波动幅度为1.8％。提出的椭圆度测量方法使椭圆度变化幅度约为0.65％, 减小了光强波动对测量精度的影响。实验显示, 构建的测量系统可满足椭圆度测量的要求。

On the basis of the requirements of cavity adjustment completed by measurement ellipticity, an ellipticity measurement system with double beam paths was researched for adjusting the cavity of a ring gyro laser. The frequency response characteristics of a square ring resonator to the S line polarized light and P line polarized light were analyzed, and the S line polarized light was chosen to stabilize the frequency of a positive resonant cavity. By inputting the S polarized beam to improve the frequency stability accurately, a frequency stabilization system and a ellipticity measurement system with double beam paths were established. By utilizing the new frequency-stabilization system and measurement methods, the frequency stabilization of the system can be realized in 10 s and the stabilization accuracy is better than 1.8%. Furthermore, the fluctuation of ellipticity has been 0.65% by the proposed method, which reduces the effect of light fluctuation on the measurement accuracy. In conclusion, the proposed system meets the needs of ellipticity measurement.