Waveplates are used in the synthesis and analysis of polarized light. Quarter Waveplates transform linearly polarized light into circularly polarized light, and vice-versa. Half Waveplates rotate the plane of polarization of linearly polarized light through any angle. They also convert left circularly polarized light into right circularly polarized light, and vice-versa.
Zero-Order Waveplates are made from two Crystalline Quartz or Sapphire plates of similar thickness, that are optically contacted together with orthogonally aligned optical axes.
Retardation varies slowly with wavelength, thus they are useful with tunable or broadband sources. Retardation is a function of thickness difference between the two plates, and is essentially invariant with temperature.