Effect of annealing on the light absorption in sapphire

Alexandrovski, Alexei L.; Fejer, Martin M.; Route, Roger K.
June 2000
AIP Conference Proceedings;2000, Vol. 523 Issue 1, p395
Academic Journal
Photothermal common-path interferometry has been used to measure optical absorption at 1064 nm and at 514 nm in high purity sapphire crystals. In as-grown and hydrogen-annealed material, uniform optical absorptions of 40–50 ppm/cm were found throughout. In a sample that had been oxygen-annealed after polishing, spatial variations in absorption and scattering/fluorescence revealed a -4 mm thick ‘skin’ of lossy material surrounding a core having lower losses typical of as-grown material. A ‘valley’ with optical absorption about 2–4 times lower than as-grown material (at both 1064 nm and 514 nm) was found at the interface between the oxidized surface layer and the core. The mechanism by which the ‘valley’ formed is not known, but it does suggest that a better understanding of the oxidation process may lead to a reduction in the optical absorption of sapphire crystals. © 2000 American Institute of Physics.


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