Photoelasticity phenomenon

Birefringence can be produced by mechanical stress exerted on optically isotropic media like glass and cubic crystals. Devices based on this phenomenon are used for polarization modulators. The so called photoelastic modulators (PEM) are widely used for measuring circular dichroism. The mechanical stress in the PEMs is produced by... 

This phenomenon is the basis for the photoelasticity method of studying inner stresses in transparent materials. 

An important phenomenon observed in amorphous plastics (also observed in optical glass) is the development of optical anisotropy due to stress. The stress-optical characteristic of transparent plastics is the basis of the important technique of photoelasticity by which stress and strain in complicated shapes, for which no analytical solution is readily available, can be determined experimentally and simply. 

Photoelasticity An experimental technique for the measuianent of stresses and strains in material objects by means of the phenomenon of mechanical birefringence. 

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