环形腔中背向散射特性的理论研究

研究了连续激光注入时无源环形腔的背向散射特性。首先，分析了注入光与无源腔频率完全匹配时，正向光和背散光振幅的稳态解，以及充光和快速关断过程中正向光和背散光振幅随时间的演化。其次，推导了无源腔中正向光和背向散射光的峰值半宽。最后，讨论了正向光和背散光随注入光频率扫描速度的变化。发现在环形腔中，总背向散射光强要比单圈背向散射光强大，背向散射光的峰值半宽为正向光的0.64倍。这些发现对背向散射精密测量、扫频法测腔损具有一定的参考作用。

Theoretical study on backscattering properties in the ring cavity

In order to reduce the influence of backscattering on the ring laser gyro, backscattering properties in the passive ring cavity was investigated. First, stable solutions of forward and backscattering light intensity and their temporal evolutions for quick turn-on and turn-off of incident light were obtained. Second, full width at half maximum of forward and backscattering light in the ring cavity as a function of incident laser frequency was derived. In the end, variation of forward and backscattering light as a function of incident laser frequency with different frequency scanning speed was discussed. It is found that the whole backscattering intensity is much larger than the single round backscattering intensity and full width at half maximum of backscattering light intensity is 0.64 times of forward light intensity. These findings are of some help to the measurement of backscattering as well as measurement of cavity loss using laser frequency scanning.