Comparison of geometric optics approximation and integral method for reflection and transmission from microgeometrical dielectric surfaces.

The effects of incidence angle, geometrical shape, and optical properties of dielectric rough surfaces on reflectivity and transmissivity are discussed. Radiative properties for various surface geometries are calculated. Since the integral method is computationally expensive, a geometric optics approximation is developed. The regions of validity of the approximation compared with the integral method are quantified. Curves are presented that show these radiative properties versus the correlation length at incidence angle for a fixed rms deviation of the surface. The surface geometry, incidence angle, multiple scattering, shadowing effects, and dielectric permittivity contributions to the domains of validity of the approximation method are discussed for both TE and TM polarizations.