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Proceedings Paper

High accuracy, absolute, cryogenic, refractive index measurements of infrared lens materials for JWST NIRCam using CHARMS
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Paper Abstract

The refractive optical design of the James Webb Space Telescope (JWST) Near Infrared Camera (NIRCam) uses three infrared materials in its lenses: LiF, BaF2, and ZnSe. In order to provide the instrument's optical designers with accurate, heretofore unavailable data for absolute refractive index based on actual cryogenic measurements, two prismatic samples of each material were measured using the cryogenic, high accuracy, refraction measuring system (CHARMS) at NASA's Goddard Space Flight Center (GSFC), densely covering the temperature range from 15 to 320 K and wavelength range from 0.4 to 5.6 microns. Data reduction methods are discussed and graphical and tabulated data for absolute refractive index, dispersion, and thermo-optic coefficient for these three materials are presented for selected wavelengths and temperatures along with estimates of index uncertainty. Coefficients for temperature-dependent Sellmeier fits of measured index are also presented with an example of their usage to predict absolute index at any wavelength or temperature within the applicable range of those parameters.

Paper Details

Date Published: 18 August 2005
PDF: 12 pages
Proc. SPIE 5904, Cryogenic Optical Systems and Instruments XI, 59040O (18 August 2005); doi: 10.1117/12.619306
Show Author Affiliations
Douglas B. Leviton, NASA Goddard Space Flight Ctr. (United States)
Bradley J. Frey, NASA Goddard Space Flight Ctr. (United States)
Todd Kvamme, Lockheed Martin Corp. (United States)

Published in SPIE Proceedings Vol. 5904:
Cryogenic Optical Systems and Instruments XI
James B. Heaney; Lawrence G. Burriesci, Editor(s)

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