Zero Order Wave plate

A waveplate (or retarder) is an optical device that alters the polarization state of light passing through it. It is made from a birefringent material, which has different refractive indices for different polarizations of light. This difference slows down one polarization component relative to the other, introducing a phase shift (or retardation) between them. Common types include quarter-wave plates (which create circular polarization) and half-wave plates (which rotate the direction of linear polarization).