Abstract: A rugate filter (10) having suppressed harmonics includes a layer (18) of material disposed on a surface (14) of an optical substrate (12) having an index of refraction versus thickness profile that is the superposition of a principle sinusoid and a secondary sinusoid. The secondary sinusoid being superimposed about -90 degrees out of phase with the principle sinusoid.

Abstract: An optical filter (10) has a radiation receiving surface, the filter including a rugate reflection filter having a reflection wavelength characteristic varies along an axis of the radiation receiving surface. The optical filter includes a plurality of serially disposed rugate coatings (10b, 10c) and has a wavelength rejection gradient that exhibits a linear, logarithmic, or power function of wavelength rejection as a function of position on the radiation receiving surface. Two or more rugate subfilms may overlap one another, or none of the rugate subfilms may overlap. The filter has a first optical density associated with a first one of the subfilms, a second optical density associated with a second one of the subfilms, and, for overlapping spectral ranges, a third optical density within a region wherein at least two subfilms overlap one another. The third optical density is a summation of the first optical density and the second optical density.

Abstract: A broadband rugate filter (10) includes an optical substrate (12) having first and second surfaces, (14, 16) and a layer (18) of optical material deposited on one of the surfaces, (14, 16). The layer (18) has an index of refraction versus thickness profile having a frequency that continuously changes in a single direction.

Abstract: An optical system (20) includes an optical filter (10) having a radiation receiving surface. The filter including a rugate reflection filter having a reflection wavelength characteristic that varies along an axis of the radiation receiving surface. The optical filter includes a plurality of serially disposed rugate coatings (10b, 10c) and has a wavelength rejection gradient that exhibits a linear, logarithmic, or power function of wavelength rejection as a function of position on the radiation receiving surface. The filter has a first optical density associated with a first one of the subfilms, a second optical density associated with a second one of the subfilms, and, for overlapping subfilms, a third optical density within a region wherein at least two subfilms overlap one another. The third optical density is a function of the first optical density and the second optical density. The filter is translated along one or more axes thereof for providing a tunable rejection of incident laser threat radiation.