Polarization properties of zeroth order surface-relief gratings with application to optical storage heads.

Abstract

A rigorous model for treating diffraction from arbitrary profile surface-relief gratings is developed. This model is valid for conical incidence geometries and elliptically polarized incident beams. The model is based on the coupled-wave method of Moharam and Gaylord (J. Opt. Soc. Am. 73, 1105-1112 (1983); J. Opt. Soc. Am. 72, 1385-1392 (1982)). The slow convergence of this model for p polarized incident light is analyzed. The source of this slow convergence is determined to be the use of Fourier series expansions for the permittivity and fields in the grating region. The polarization and energy distribution properties of zeroth order gratings are summarized. Designs are presented for zeroth order gratings that function as retardation and polarization conversion elements for specularly reflected beams. Photoresist gratings are fabricated and characterized by ellipsometric techniques to confirm the predictions of the coupled-wave model and to demonstrate these novel designs. The application of zeroth order gratings to optical storage heads is discussed, and novel head designs based on these components are presented.