去除光学器件弹光双折射的方法

摘要

在电光、磁光调制器和传感器等光学器件的制作和使用过程中,经常会产生影响器件性能的弹光双折射。根据折射率椭球分析法,通过系统分析各晶系晶体的弹光效应,提出了若干去除光学器件中静态弹光双折射的方法。主要结论包括：对于正交晶系的双轴晶体,当光波沿着晶体任意一个主轴方向传播时,如果作用于晶体另外两个主轴方向的应力能够满足某一与晶体自身参数有关的倍数关系且不存在剪切应力,则可以去除这两个应力引起的弹光双折射；对利用所有单轴晶体,¯43m,432, m3m点群的立方晶体和匀质光学玻璃制作的光学器件,如果能够保持晶体沿着x1, x2轴方向的正应力相等且不存在剪切应力,或只对晶体施加x3方向的正应力,也可以避免沿着晶体主光轴x3方向传播光波的弹光双折射。上述去除弹光双折射的方法对光学器件的设计、制作和使用具有重要参考价值。%There often appears unwanted elasto-optical birefringence in optical devices such as electro-optical, magneto-optical modulators and sensors when they are manufactured and used. This kind of elasto-optical birefringence causes unwanted effect for optical device and needs to be removed. Based on the method of index ellipsoid analysis, we theoretically analyze elasto-optical effects in various point groups of optical crystals and glasses, and accordingly propose some methods to eliminate unwanted elasto-optical birefringences in optical crystals and glasses. Main conclusions show that for orthorhombic biaxial crystal and the light wave propagating along any one crystalline axis of the crystal, if there is no shearing stress and the two external normal stresses applied to the other two crystalline axes can keep a constant ratio related to crystal parameters including refractive index and photoelastic constants, then unwanted elasto-optical birefringence can be eliminated from relevant optical devices, typical crystals include potassium titanium oxide phosphate (KTiOPO4, KTP) crystal and rubidium titanium oxide phosphate (RbTiOPO4, RTP) crystal, which are usually used as electrooptic Q-switchers in laser systems. For all the uniaxial crystyals such as potassium dihydron phosphate (KH2PO4, KDP), beta-barium borate (β-BaB2O4, BBO) and lithiun niobate (LiNbO3, LN) crystals, cubic crystals of ¯43m, 432, m3m point groups such as bismuth germanate (Bi4Ge3O12, BGO) crystal, and optical glasses, if the two normal stresses applied to the x1-and x2-crystalline axes of the crystal are equal to each other and there is no shearing stress, or there exists only one normal stress applied to the x3-crystalline axis of the crystal, then for the light wave propagating along the x3-crystalline axis, unwanted elasto-optical birefringence in relevant optical devices can also be eliminated. The above-proposed method to remove unwanted elasto-optical birefringence is benificial to design, manufacture, and usage of related optical devices.