Birefringence Measurement
Birefringence Measurement
Birefringence is an intrinsic material property. A material with linear birefringence has different refractive indices for (orthogonal) linear polarized light beams passing through it. The integrated effect along a light path passing through a bulk sample is called retardation or retardance.
Manufactured optical displays represent one example of a particularly important area of birefringence. Isotropic materials such as glass do not exhibit birefringence unless the material is subjected to stress. The stress may be externally induced or it may be internal stress, induced during the manufacture of the material sample. The photoelastic modulator (PEM) offers an extremely sensitive method of measuring low levels of retardation arising from stress in an optical material sample.