Date of Award

6-1-2014

Document Type

Campus Access Thesis

Degree Name

Master of Science (MS)

Department

Physics, Applied

First Advisor

Steven Arnason

Second Advisor

Walter Buchwald

Third Advisor

Greg Sun

Abstract

Recently significant efforts have been made to develop a high performance mid-wave infrared imaging sensor that can be operated at temperatures greater than 180K. Above 180K the infrared imager can use thermoelectric cooler instead of the expensive, higher power, and shorter lifetime stirling coolers that are typically used. Operating high-performance mid-wave infrared detectors at 180K is not currently possible with the traditional analog readout integrated circuits. At high operating temperatures the mid-wave detectors have an increase of background current (dark current). The dark current combines with the photon current and is stored together on the readout. This is problematic because traditional analog readouts have a limited electron storage capacity and therefore the storage capacity fills up faster. The resulting reduced collection time lowers the sensitivity of the device. The infrared community has made significant investments to develop a detector material that has a lower dark current at 180K. This work examines the capability of the digital-pixel readout developed at M.I.T. Lincoln Laboratory as an alternative approach. The digital-pixel readout has shown an increase of up to 3 orders of magnitude in storage capacity than the traditional analog readout [1]. This significant increase in dynamic range enables the digital-pixel readout to handle the excess dark current at 180K. The digital-pixel readout has been tested at 180K with standard HgCdTe mid-wave detectors. An array median noise equivalent differential temperature of 25mK has been measured. If the same detectors were mated to a traditional analog readout, the theoretical performance would be between 50 - 60 mK.

Comments

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