Muscovite Sheet Mica of ASTM (D-351-97) V-I, having an even surface that is optically flat, transparent, scratch-less and free from finger prints, is specially used for Broadband Wave plates or Retardation Plates.
These useful broadband wave plates are manufactured by cleaving crystalline sheet mica to quarter, half and full wave plates getting the precise first order retardation at 550mm wavelength. These are useful throughout the visible spectrum from 400 to 700nm. The single Mica Disk is sandwiched between optical glass disks for protection on both sides and is oriented so that the optical axes are orthogonal. These broadband mica wave plates are produced in many diameter sizes of varied thickness.
Mica has birefringent properties, which means that it can split and divide unpolarized incident light into two orthogonal linearly polarized beams at different velocities, one transmitting straight through, the second precisely separated by 90o. Beamsplitting polarizers are used after the generation of the laser and different degrees of retardation are produced by mica wave plates.
Mica has excellent polarization properties including very high extinction ratio and transmitting efficiency and helps to reduce light transmission in the above applications. Mica also exhibits extremely broadband transmission performance, and these mica wave plates can be operated with a high degree of retardation accuracy over a broad wave-length range.