FORM BIREFRINGENCE OF SURFACE RELIEF GRATINGS AND ITS ANGULAR-DEPENDENCE

High spatial frequency dielectric surface relief gratings can be applied as polarization elements and as antireflection layers. The characteristic properties of a grating are calculated numerically using the rigorous coupled wave method. These calculations are compared with experimental results from a holographically recorded sinusoidal surface-relief grating made in photoresist. The influence of the polarization (often described in terms of "form birefringence") is investigated with respect to the incidence. We verify that, in the presence of diffracted orders orders, the behaviour differs from that of a uniaxial crystal, that is expected for gratings with periods small compared to the wavelength.