Summary: Understanding the residual stress birefringence characteristics of both individual components and bulk materials is critical for researchers, quality control professionals and factory managers responsible for products ranging from precision optics to high volume consumer devices.
Residual stress in optical transparent materials often manifests itself as a polarization-dependent optical property, such as linear birefringence. Birefringence, or the double refraction of light, is a common natural characteristic of many crystals and other anisotropic materials such as calcite and mica. Isotropic materials such as fused silica, commercial glass (including both float glass and fusion glass) and many plastics have a uniform index of refraction in all directions and do not exhibit native birefringence. However, whenever mechanical stress is applied to isotropic materials, residual birefringence is generated. This birefringence is linearly-proportional to the stress in the material. If the material thickness and stress-optic coefficient of the material are known, the birefringence can be used to calculate the residual stress, which is typically stated in units of pressure, such as MPa or psi. Because the relationship is linear, birefringence magnitude can be substituted for actual stress (i.e. high birefringence = high residual stress).
Residual Stress Birefringence in Optical Materials - PDF 0.7 Meg