激光陀螺本征模偏振态与磁敏感特性的理论研究

Theoretical analysis of polarization eigenstate and magnetic sensitivity in a ring laser gyro

环境磁场的干扰是影响激光陀螺精度的重要因素之一.为了减小二频机械抖动激光陀螺的磁敏感性,推导了环形腔的琼斯矩阵,其中考虑了非共面角、增益介质、腔损耗、腔镜反射各向异性和应力双折射,采用矩阵本征问题求解的摄动理论分析了环形腔的偏振态和磁敏感特性.研究表明,为了减小激光陀螺的磁敏感性,应减小非共面角和腔损耗,增大腔镜的反射各向异性.腔镜应力双折射究竟会增大还是减小磁敏感性与应力作用主轴、受应力腔镜的位置有关,此外它还会引起顺时针和逆时针模式之间的偏振非互易性.磁敏感性与腔失谐近似成线性关系,导致激光陀螺工作于增益峰值时磁敏感性并非最小.这些结果对减小二频机械抖动激光陀螺的磁敏感性具有较好的指导意义.

Disturbance by ambient magnetic field is an important factor, which leads to measurement error of the laser gyro. In order to reduce the magnetic sensitivity, the polarization eigenstate in ring cavity is analyzed with matrix perturbation method, considering factors of small nonplanarity, mirror anisotropy and stress birefringence, gain and so on. The main factors affecting the magnetic sensitivity of the laser gyro are discussed. Ellipticities of eigen modes in clockwise and anti-clockwise direction caused by nonplanarity are identical and both are proportional to magnetic sensitivity. The influence of stress birefringence on ellipticity is related to mirror position, propagating direction of eigenmodes and main axis of stress. Nonplanarity is zero when ellipticities of eigen modes in clockwise and anti-clockwise direction are equal without stress birefringence in the passive cavity. A lower cavity loss is better to reduce the magnetic sensitivity of the laser gyro. The miriimum magnetic sensitivity is not identical with peak gain for the laser gyro. Large phase and amplitude anisotropies of mirrors are useful to reduce magnetic sensitivity and ellipticity. These findings are significant for the reduction of magnetic sensitivity in ring laser gyros.