The major parameters of a crystalline colloidal array optical filter have been investigated theoretically, and the results compared to published experimental data. This filter consists of an aqueous suspension of polystyrene spheres in a lattice which produces Bragg diffraction of incident light. The development of expressions for the filter bandwidth and attenuation utilized both dynamical x-ray diffraction theory and light scattering theory. The theoretical attenuation function indicates that extremely high absorbance values are achievable with relatively thin filters.

The colloidal array filter consists of an aqueous suspension of polystyrene spheres arranged in a crystalline lattice, thereby producing Bragg diffraction of incident light. Recent measurements have shown that a rejection filter incorporating a thin layer of the colloidal suspension has a moderately narrow bandwidth and unusually large peak absorbance.1 We have successfully explained these results using both dynamic x-ray diffraction theory and optical scattering theory. The theoretical bandwidth is in good agreement with the experimental value, while the theoretical attenuation results are consistent with measured transmittance values. The theoretical attenuation function indicates that actual filters may be constructed that are thinner and more efficient than the first experimental ones. The theoretical angle shift of the rejection band maximum has also been calculated and is in excellent agreement with experimental data.