Title

Evaporation of uniform antireflection coatings on hemispherical lenses to enhance infrared antenna gain

Authors

Authors

B. A. Slovick; P. M. Krenz; G. Zummo;G. D. Boreman

Comments

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Abbreviated Journal Title

Infrared Phys. Technol.

Keywords

Infrared antennas; Immersion lens; Antenna-coupled detectors; Antireflection coatings; SURFACE; Instruments & Instrumentation; Optics; Physics, Applied

Abstract

Infrared dipole-coupled bolometers receive radiation more efficiently when illuminated through a high permittivity, antireflection (AR) coated, hemispherical immersion lens. To maintain the enhanced responsivity for all illumination angles, the AR coating Must be uniform over the hemispherical surface. An evaporation method for depositing a uniform AR coating on the hemispherical surface is presented. The lens is tilted relative to the source, which can be either electron-beam or thermal, and rotated throughout the deposition. Evaporation at an angle of 70 degrees yields a uniform film with less than 10% thickness variation over a 120 degrees full angle of the hemispherical Surface. A theoretical model is developed and compared to profilometer measurements. In all cases, there is general agreement between theory and measurement. A single dipole is fabricated onto the flat surface of an AR-coated germanium immersion lens and the responsivity is measured for both substrate-side and air-side illumination. With a zinc sulfide (ZnS) single-layer AR coating, substrate-side illumination yields a broadside antenna response 49 +/- 2.7 times greater than air-side illumination. (C) 2009 Elsevier B.V. All rights reserved.

Journal Title

Infrared Physics & Technology

Volume

53

Issue/Number

2

Publication Date

1-1-2010

Document Type

Article

Language

English

First Page

89

Last Page

93

WOS Identifier

WOS:000275849800003

ISSN

1350-4495

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