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Proceedings Paper

Detection of subsurface damage: studies in sapphire
Author(s): David R. Black; Robert S. Polvani; Linda M. Braun; Bernard J. Hockey; Grady S. White
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Paper Abstract

A variety of nondestructive characterization techniques has been used to detect and measure subsurface damage in single- crystal sapphire to develop methods suitable to inspect high performance optics for sub-surface damage. These techniques include polarized light microscopy, x-ray diffraction topography, transmission electron microscopy (TEM) and Raman spectroscopy. TEM examination shows that for ground surfaces damage can extend up to 6 - 7 micrometers into the bulk and includes cracks, twins and dislocations, while under polished surfaces only dislocations are seen. X-ray diffraction topography can image defects such as long-range strain, dislocations, residual surface scratches (not visible optically) and low-angle grain boundaries (lineage). Polarized light is also sensitive to strain and provides a relatively easy method for detecting defects such as cracks and lineage. Of all of the techniques Raman spectroscopy offers the best potential for quantifying strain in terms of stress.

Paper Details

Date Published: 27 June 1997
PDF: 13 pages
Proc. SPIE 3060, Window and Dome Technologies and Materials V, (27 June 1997); doi: 10.1117/12.277036
Show Author Affiliations
David R. Black, National Institute of Standards and Technology (United States)
Robert S. Polvani, National Institute of Standards and Technology (United States)
Linda M. Braun, National Institute of Standards and Technology (United States)
Bernard J. Hockey, National Institute of Standards and Technology (United States)
Grady S. White, National Institute of Standards and Technology (United States)


Published in SPIE Proceedings Vol. 3060:
Window and Dome Technologies and Materials V
Randal W. Tustison, Editor(s)

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