入射光偏振方向对LiNbO3晶体近光轴电光调制的影响

分析了在垂直LiNbO3晶体光轴方向加电压，光沿近光轴方向传播时，入射光偏振方向对电光调制器的影响。通过计算加电场后双折射光程差的变化和偏光振动方向的转动，画出在正交偏振镜下不同起偏方向的锥光干涉图，得到干涉图随起偏方向变化的规律：由偏光振动方向转动引起的消光区域随起偏方向的转动而转动，在起偏和检偏方向上始终消光，在与起偏方向成±45°角方向始终全透光，并且消光线的交点即感应双光轴头不随起偏方向的转动而变化，始终在折射率变大的感应主轴上。

The electro-optic effect in LiNbO3 crystal has been analyzed for light propagating near the optic axis with any polarization direction and for an electric field direction perpendicular to the optic axis. The passive and the electrically induced birefringences and the rotation of polarization direction have been calculated, and the conoscopic interference figures under orthogonal polariscopes for different polarization directions and a field in x-axis of LiNbO3 have been plotted. The extinction areas caused by the rotation of polarization direction change with the polarization direction of light, but the two heads of the induced optical axes do not vary, which are always on the induced principal axis with bigger refractive index. The directions of polariscopes are always extinction, and the ±45° directions with polariscopes always have the maximum intensity. The conoscopic interference figures have been demonstrated experimentally by rotating polariscopes directions, which are accord with the theoretically calculating plots.