Birefringence Measurement

Birefringence is a difference in refractive index that occurs along different axes in a material. In crystals such as calcite this is an intrinsic effect resulting from the atomic structure. The result is that light travelling along one axis experiences a different refractive index than light travelling along a different axis. There is an excellent tutorial created by András Szilágyi that illustrates birefringence and other concepts.

In addition to atomic structure there are other physical phenomena that cause birefringence in materials. For example in polymeric materials such as plastics the molecular structure is normally isotropic. However, manufacturing processes, such as extrusion and injection molding, create anisotropies in the material which lead to physical stress and optical birefringence.

Further Birefringence Discussions:

Birefringence Measurement Application Note

White Paper – Residual Stress Birefringence in Optical Materials

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