2 February 2015

Northwestern demonstrates MWIR imaging at high temperature

Researchers at Northwestern University's Center for Quantum Devices (CQD) have developed an indium arsenide/gallium antimonide (InAs/GaSb) type II superlattice that demonstrates high-resolution mid-wavelength infrared (MWIR) imaging while operating at high temperatures (Chen et al, Optics Letters, vol. 40, issue 1, p45-47 (2015)).

MWIR radiation (with a wavelength of 3-5μm) has a wide range of applications, from aerial surveillance to cancer detection. As the uses for high-sensitivity, high-resolution imaging continue to expand, MWIR sources are becoming more attractive.

However, currently, commercial technologies for MWIR detection, such as indium antimonide (InSb) and mercury cadmium telluride (MCT), can only operate at cryogenic temperatures in order to reduce thermal and electrical noise.

"A higher operating temperature eliminates the need for liquid nitrogen," says Manijeh Razeghi, the Walter P. Murphy Professor of Electrical Engineering and Computer Science and director of the CQD. "That makes detectors more compact, less expensive, and more portable," she adds.

In Northwestern's device, a 320×256-pixel unipolar focal plane array (FPA) using pMp architecture exhibited what was reckoned to be excellent infrared imaging from 81 to 150K as well as about 98% operability, illustrating the possibility for high-temperature operation. At 150K and −50mV operation bias, the 27μm pixels exhibited dark current density of 1.2×10−5A/cm2, with 50% cutoff wavelength of 4.9μm, quantum efficiency of 67% at peak responsivity (4.6μm), and specific detectivity of 1.2×1012 Jones.

With MWIR cameras being capable of passive infrared imaging, Northwestern says that its new technique was particularly successful at obtaining infrared images of the human body, which has potential for vascular imaging and disease detection.

The research was supported by US Defense Advanced Research Projects Agency (DARPA), the Army Research Laboratory, Air Force Research Laboratory, and NASA.

Tags: MWIR IR detectors

Visit: www.opticsinfobase.org/ol/abstract.cfm?uri=ol-40-1-45

Visit: http://cqd.eecs.northwestern.edu