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Proceedings Paper

Refractive index of infrared-transparent polycrystalline alumina
Author(s): Daniel C. Harris; Linda F. Johnson; Lee R. Cambrea; Lawrence Baldwin; Meghan Baronowski; David E. Zelmon; William B. Poston; John D. Kunkel; Mark Parish; Marina R. Pascucci; John J. Gannon; Tzu-Chien Wen
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Paper Abstract

The refractive index of polycrystalline α-alumina prisms with an average grain size of 0.6 μm is reported for the wavelength range 0.9 to 5.0 and the temperature range 293 to 498K. Results agree within 0.0002 with the refractive index predicted for randomly oriented grains of single-crystal aluminum oxide. This paper provides tutorial background on the behavior of birefringent materials and explains how the refractive index of polycrystalline alumina can be predicted from the ordinary and extraordinary refractive indices of sapphire. The refractive index of polycrystalline alumina is described by

𝑛𝑛2 − 1 = (A+B [𝑇𝑇2−𝑇𝑇20]) +Dλ2 /λ2−(λ1+C [𝑇𝑇2−𝑇𝑇20])2 + λ2−λ22

where wavelength λ is expressed in μm, To = 295.15 K, A = 2.07156, B = 6.273× 10-8, λ1 = 0.091293, C = –1.9516 × 10-8, D = 5.62675, and λ2 = 18.5533. The slope dn/dT varies with λ and T, but has the approximate value 1.4 × 10-5 K-1 in the range 296–498 K.

Paper Details

Date Published: 3 May 2017
PDF: 11 pages
Proc. SPIE 10179, Window and Dome Technologies and Materials XV, 101790F (3 May 2017); doi: 10.1117/12.2257580
Show Author Affiliations
Daniel C. Harris, Naval Air Systems Command (United States)
Linda F. Johnson, Naval Air Systems Command (United States)
Lee R. Cambrea, Naval Air Systems Command (United States)
Lawrence Baldwin, Naval Air Systems Command (United States)
Meghan Baronowski, Naval Air Systems Command (United States)
David E. Zelmon, Air Force Research Lab. (United States)
William B. Poston, Air Force Research Lab. (United States)
John D. Kunkel, Air Force Research Lab. (United States)
Mark Parish, CeraNova Corp. (United States)
Marina R. Pascucci, CeraNova Corp. (United States)
John J. Gannon, CeraNova Corp. (United States)
Tzu-Chien Wen, The Univ. of Utah (United States)


Published in SPIE Proceedings Vol. 10179:
Window and Dome Technologies and Materials XV
Brian J. Zelinski, Editor(s)

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