The applications for wave plates are many and varied. They can find use in areas such as power attenuation of a laser and optical isolation. In biomedical applications, wave plates are used to determine the polarization of body fluids in microscopes and to correct for unwanted phase shifts. They are also used in astronomy, in the semiconductor industry and in aerospace. In short, almost every application that requires polarized light uses a wave plate to control polarization. The materials used for them are determined by the application. These options include a wide array of birefringent crystalline materials, total internal reflection retarders, polymer retarders and liquid crystals.
How a wave plate works
A wave plate produces a phase shift between the two orthogonal polarizations of a light wave. This is done via birefringence, or when the index of refraction along the slow axis differs from that along the fast axis. Common wave-plate retardances include quarter- and half-wave plates. The quarter-wave plate turns linearly polarized light into circularly polarized light with the input light at a 45° angle between the fast and slow axes. The half-wave plate is a polarization rotator as it flips the polarization direction around the fast axis of the retarder. These are manufactured from various materials, depending on the application, with costs ranging from tens to thousands of dollars.
This article comes from photonics edit released