系统研究入射光为不同偏振态时的准相位匹配线性电光效应。在准相位匹配条件满足时, 若入射光为线偏振光, 则o光与e光能够彻底耦合, 出射光仍为线偏振光, 且其偏振方向可以通过外加电场调节到任意角度; 若入射光为椭圆偏振光, 则o光与e光不能彻底耦合, 输出光为与输入光同椭圆率的椭圆偏振光, 其椭圆方位角可以通过调节外加电场旋转到任意角度; 若入射光为圆偏振光, 则o光与e光之间没有能量耦合, 输出光仍为圆偏振光。准相位匹配条件满足的线性电光效应在保偏的偏振旋转器中有重要应用。在准相位匹配条件不满足时, o光与e光由于相位失配而没有能量耦合, 输出光的偏振态取决于o光与e光的初始相位差和双折射(自然双折射和电光双折射)引起的附加相位差, 特别是极化占空比为0.5时, 电光效应引起的双折射总效果为零。

Quasi-Phase-Matched (QPM) linear electro-optic effect is investigated when the incident light is of different polarization. The study shows the electro-optic coupling is influenced by the polarization remarkably. For the case that the QPM condition is satisfied, when the input light is linearly polarized, the energies of o-ray and e-ray can be coupled to each other totally, and the polarization direction can be rotated at any angle by external electric field; when the input light is of ellipsoidal polarization, the coupling between o-ray and e-ray is not complete while the azimuth angle of ellipsoid can also be rotated at any angle; when the input light is circularly polarized, there is no electro-optical coupling between o-ray and e-ray, and polarization of the output light keeps unchanged. For the case that QPM condition is not satisfied, the light propagating along PPLN is just as propagating along a normal birefringent crystal. The electro-optic effect makes no contribution to the birefringence when the poling duty cycle D is equal to 0.5.