MICA

When any form of polarized light is incident on a birefringent waveplate, it is resolved into two linearly polarized components which vibrate perpendicular to each other and travel with different velocities in the crystal. The beams emerge with a phase delay. This phase delay or retardation is dependent on birefringence of the crystal. Birefringence at a specified wavelength is the difference in refractive indices of the extraordinary and ordinary resolved components. Because of dispersion of birefringence i.e. it's dependence on wavelength, there is a variation of retardation with wavelength.

Quarter and half wave mica waveplates are available as a thin cleaved zero order retarder at a specified wavelength between 450 to 1600 nm cemented between BK7 glass plates or as bare mica, V type anti-reflection coated and mounted in a cell. Mica is a bi-axial, optically inactive crystal which has about 3 to 5 % absorption in the visible region of the spectrum. The cemented mica retarders are available in clear aperture diameters of 10 and 22 mm while bare mica retarders are available in a clear aperture diameter of 25 mm only. Special sizes are available upon request.