Transparent plates with a defined birefringence, used for modifying the Polarization of light.
Optical waveplates (also called wave plates or retarder plates) are Transparent plates with a carefully adjusted birefringence, which are mostly used for manipulating the polarization state of Light beams. A waveplate has a slow axis and a FAST axis, both being perpendicular to the surface and the beam direction, and also to each other. The Phase Velocity of light is slightly higher for polarization along the fast axis. The designed value of optical retardance is achieved only in a limited WavelengthRange and in a limited range of incidence angles.