Question

Can I get an explanation on what Strain/stress-induced Birefringence is and how it works?

Answer 1

Stress in optical materials commonly presents itself by generating an anisotropy in the material (Stress-Induced birefringence). Measuring the birefringence, material thickness, and knowing the material's stress optic coefficient, allows the calculation of the resulting differential stress in the material. Stress in these types of materials may be permanently present resulting from stress created during the manufacturing process, such as with injection molded plastics or in polished optical materials or may be temporarily induced by applying a force to a material such as occurs in Hinds Photoelastic modulator (PEM) optical assemblies.

Stress-induced birefringence can be measured the same way other low-level birefringence is measured which is based on a system of photoelastic modulator.