What is birefringence?
The phenomenon of double refraction of light wavefronts in a transparent, molecularly ordered material produced by the existence or orientation-dependent differences in refractive index. The term birefringence also commonly refers to the refractive index difference experienced by a transmitted wave through such a material. Wavefronts of light incident on a birefringent specimen are split into ordinary (no) and extraordinary (ne) components that can recombine after emergence from the specimen to produce linearly, elliptically, or circularly polarized light.
