Integrated multicolor detector utilizing 1D photonic bandgap filter with wedge-shaped defect

Abstract

We propose a single-chip multicolor photodetector for (3-5) μm range based on a linear IR semiconductor detector array with an integrated 1-D photonic bandgap (PBG) filter. A wedge-shaped defect slab (corresponding to a Fizeau-type interferometer) is introduced into the filter instead of one of the layers. The bandgap of the photonic crystal coincides with the spectral sensitivity range of the photodetector array, while the built-in defect gives a transmission peak within the same range. The defect thickness varies along the array length and thus shifts the transmission peak wavelength. The optimized photonic bandgap filter including defect is designed using the transfer matrix method. The peak frequency is tuned by choosing the geometrical parameters of the wedge-shaped defect. In our experiments, thin alternating Si and SiO 2 films are sputtered onto the array surface, thus forming a 1-D PBG structure. The defect is fabricated by gradually changing the middle Si layer thickness over the width of the array. Its wedge-forming is performed by micromachining or, alternatively, by in-situ oblique deposition within the sputtering system and, possibly, subsequent chemomechanical polishing. The characteristics of the finished PBG structure are measured using an IR spectrophotometer. An increase of the number of PBG layers improves the confinement of transmission peaks and thus decreases the crosstalk between the array elements. Although our multicolor detector is designed for the (3-5) μm atmospheric window, it can be straightforwardly redesigned for any other optical range.