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Broadband Infrared Antireflection Structured Silicon SurfacesSilicon and germanium are materials often used for infrared (IR) windows and optical elements. However they have a very high index of refraction, in the order of three to four, which causes large reflection losses on each surface. These losses are especially high under large angles of incidence which are often desirable if signals are faint and fast optics are to be used. Solid antireflection coatings are either not available because materials with appropriate index of refraction do not exist, or their use is limited to a small wavelength range and small angles of incidence. We will present the status of our work to calculate, create, and test the performance of graded structures in Si to reduce its surface reflection. The structures are expected to work over the very broad wavelength range of 10 micron to 1000 micron and a wide range of angle of incidence. We.have identified several high aspect ratio MEMS process techniques to create the structures and have done 3D electromagnetic modeling, which predicts significant effects. Measurements on different samples have validated our modeling.
Document ID
19990103094
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Stewart, Kenneth
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Fettig, Rainer
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Allen, Christine
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Larocque, Jennifer
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Date Acquired
August 19, 2013
Publication Date
January 1, 1999
Subject Category
Optics
Distribution Limits
Public
Copyright
Other

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