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Detection of sub-surface damage: Studies in sapphire

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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. Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Abstract Text Return: Query Results Return items starting with number Query Form Database: Astronomy Physics arXiv e-prints

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