Antenna-coupled infrared detectors
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abstract
Uncooled bolometric detectors used in infrared imaging systems have slow time constants (-10 ms) which makes them impractical for fast-frame-rate applications. Antenna-coupled microbolometers are fast uncooled detectors with good sensitivity, directivity and can be polarization and wavelength selective. These detectors have collection areas in the order of 10 μm 2 which are too small for infrared imaging systems where a typical pixel area ranges from 20 × 20 μm 2 to 50 × 50 μm 2. In this paper two different types of detectors that can cover a typical pixel area are fabricated and their performance measured. The first type of IR pixel is a two-dimensional array of serially connected antenna-coupled microbolometers. These arrays can cover any pixel area and increase the signal-to-noise ratio of a single detector by a factor of N for an N×N array. The second IR pixel was fabricated by using a Fresnel Zone Plate Lens (FZPL) to collect and focus energy to a single antenna-coupled detector. An FZPL-coupled detector of 200 μm in diameter showed a 2 × increase in D* compared to single element detectors. An 8 × 8 array of antenna-coupled pixels were fabricated on a commercial ROIC, measurements made on this antenna-coupled infrared focal plane array showed that the integration of antenna-coupled detectors to a commercial ROIC is possible.
