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Proceedings Paper

Measurements of weak scattering and absorption in spinel and sapphire from the near infrared to the visible
Author(s): J. Ma; M. B. Airola; M. E. Thomas; J. B. Spicer
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Paper Abstract

Durable window materials with minimal optical loss are important for future high-energy laser (HEL) systems that will operate at or near the megawatt level. However, potential material candidates such as spinel and sapphire have scattering and absorption levels near the 1 μm wavelength region that are undesirable for future HEL applications. Indeed, absorption measurements in these materials indicate that residual loss in this region can be associated with a weak absorption tail. This tail has been experimentally characterized for amorphous semiconductor materials, long-wave infrared glasses, and certain optical fiber materials, but no comprehensive characterization has been done on crystalline window materials. Measurements of both weak scattering and absorption are essential for understanding loss mechanisms in these low loss materials. In this work, scattering measurements on spinel and sapphire samples obtained from different vendors are reported for wavelengths of 532 nm, 633 nm, 1064 nm, and 1550 nm. These measurements were obtained using a bidirectional scatterance probability distribution function instrument. The surface and bulk absorptions of these materials at wavelengths of 355 nm, 532 nm, and 1064 nm were also measured using photothermal common path interferometry. Additionally, a photoacoustic technique was used to obtain the absorption measurements at 1064 nm. In addition, ultraviolet-visible spectroscopy measurements were made to detect any impurity bands. These measurements contribute to a better understanding of the low-loss phenomenon near the 1 μm wavelength in both spinel and sapphire.

Paper Details

Date Published: 13 May 2019
PDF: 10 pages
Proc. SPIE 10985, Window and Dome Technologies and Materials XVI, 1098502 (13 May 2019); doi: 10.1117/12.2518957
Show Author Affiliations
J. Ma, Johns Hopkins Univ. (United States)
M. B. Airola, Johns Hopkins Univ. Applied Physics Lab., LLC (United States)
M. E. Thomas, Johns Hopkins Univ. (United States)
Johns Hopkins Univ. Applied Physics Lab., LLC (United States)
J. B. Spicer, Johns Hopkins Univ. (United States)

Published in SPIE Proceedings Vol. 10985:
Window and Dome Technologies and Materials XVI
W. Howard Poisl, Editor(s)

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