birefringentní

Birefringentní refers to a property of certain optical materials where the speed of light traveling through the material depends on its polarization and direction of propagation. This phenomenon, also known as optical anisotropy, occurs in materials that lack cubic symmetry, such as calcite, quartz, and many crystals and polymers. When unpolarized light enters a birefringent material, it is typically split into two rays, known as the ordinary ray (o-ray) and the extraordinary ray (e-ray). These rays travel at different speeds and, consequently, refract at different angles. The ordinary ray behaves predictably, with its refractive index being the same in all directions perpendicular to the optic axis. The extraordinary ray, however, experiences a refractive index that varies with direction. The difference in refractive indices between the o-ray and e-ray is a measure of the material's birefringence. This property is exploited in various optical devices, including polarizers, waveplates, and optical modulators, which are essential components in applications ranging from microscopy and photography to telecommunications and displays. The direction along which the refractive indices are equal for both rays is called the optic axis.