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Proceedings Paper

Micromachined optical concentrators for IR negative-luminescent devices
Author(s): Geoff R. Nash; Tim Ashley; Neil T. Gordon; T. J. Phillips; C. D. Maxey; C. L. Jones; R. A. Catchpole
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Paper Abstract

Negative luminescent (NL) devices, which to an IR observer appear colder than they actually are, have a wide range of possible applications, including for use as thermal radiation shields in IR cameras, and as IR sources in gas sensing systems. For many of these applications a large area (>1cm2) device is required, together with as large as possible apparent temperature range. However, under reverse bias significant currents are required to reduce the carrier concentrations to the levels needed for maximum possible absorption. These may lead to current heating of the device, which in turn reduces the apparent temperature range. We have therefore used a novel micromachining technique to fabricate integrated optical concentrators in InSb/InAlSb and HgCdTe NL devices. Smaller area diodes can then be used to achieve the same absorption (e.g. for InSb an area reduction of 16 is possible) and the required currents are thus reduced. To fabricate the concentrators parabolic resist masks are first produced, which are approximately 10 μm high and approximately 53 μm wide, by resist reflow at 120 degrees C. Inductively coupled plasma (ICP) etching is then used to alternately etch the resist mask and the semiconductor, with oxygen and methane/hydrogen respectively, producing concentrators with almost parabolic profiles. Currently, the concentrators are typically 30 μm high, with a top diameter of approximately 15 μm. Continuing optimization of the process to reach the theoretical limits of optical gain is described.

Paper Details

Date Published: 19 November 2001
PDF: 8 pages
Proc. SPIE 4446, Nonimaging Optics: Maximum Efficiency Light Transfer VI, (19 November 2001); doi: 10.1117/12.448818
Show Author Affiliations
Geoff R. Nash, Defence Evaluation and Research Agency Malvern (United Kingdom)
Tim Ashley, Defence Evaluation and Research Agency Malvern (United Kingdom)
Neil T. Gordon, Defence Evaluation and Researchg Agency Malvern (United Kingdom)
T. J. Phillips, Defence Evaluation and Research Agency Malvern (United Kingdom)
C. D. Maxey, BAE SYSTEMS (United Kingdom)
C. L. Jones, BAE SYSTEMS (United Kingdom)
R. A. Catchpole, BAE SYSTEMS (United Kingdom)

Published in SPIE Proceedings Vol. 4446:
Nonimaging Optics: Maximum Efficiency Light Transfer VI
Roland Winston, Editor(s)

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