EFFECTIVE-MEDIUM THEORY OF SINUSOIDALLY MODULATED VOLUME HOLOGRAMS

Zeroth-order effective-medium theory is applied to sinusoidally modula ted volume holograms for which the period of the grating is much small er than the illumination wavelength. These holograms can be modeled as negative uniaxial films, with the effective ordinary and extraordinar y permittivities being determined by the small-period quasi-static app roximation. The limits of validity of the small-period approximation a re examined as a function of the wavelength-to-grating-period ratio (l ambda:Lambda) by rigorous coupled-wave theory. The limits are shown to be more restrictive for slanted holograms and for conically incident waves than for unslanted holograms and nonconically incident waves.