Design and optimization of space-variant photonic crystal filters.

A space-variant photonic crystal filter is designed and optimized that may be placed over a detector array to perform filtering functions tuned for each pixel. The photonic crystal is formed by etching arrays of holes through a multilayer stack of alternating high and low refractive index materials. Position of a narrow transmission notch within a wide reflection band is varied across the device aperture by adjusting the diameter of the holes. Numerical simulations are used to design and optimize the geometry of the photonic crystal. As a result of physics inherent in the etching process, the diameter of the holes reduces with depth, producing a taper. Optical performance was found to be sensitive to the taper, but a method for compensation was developed where film thickness is varied through the device.