Thermal and photo-induced surface damage in paratellurite |
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Authors: | K Yasutake H Kakiuchi A Takeuchi K Yoshii H Yamada H Kawabe |
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Affiliation: | (1) Department of Precision Science and Technology, Faculty of Engineering, Osaka University, 2-1 Yamadaoka, Suita Osaka 565, Japan |
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Abstract: | Long-term operation of TeO2 acousto-optical device is limited by the formation of surface damage caused by the He–Cd laser
irradiation. Similar surface damage occurs during the heat treatment of the TeO2 crystal at 350°C. In this study, TeO2 specimens
after various surface treatments have been observed by electron microscopy and X-ray photoelectron spectroscopy. The variation
of the transmittance for mechanically polished specimens has been measured in situ during heat treatments. It was found that
the thermal surface damage at 350°C was formed in the surface layer damaged by mechanical polishing. The mechanically damaged
layer was amorphous and deficient in oxygen in the as-polished state. The electron microscopic observation revealed that the
surface damage layer induced by heat treatments or by the ultraviolet light irradiation contained tellurium particles (20–40
nm) in diameter dispersed in the TeO2 matrix. On annealing the TeO2 specimen at 500°C in air, however, the particles disappeared
because of the melting, evaporation and oxidation of tellurium which restores the transmittance of the crystal. Based on the
results, combined with the observation of surface damage induced by the visible light irradiation, a possible mechanism of
the surface damage formation has been briefly discussed.
This revised version was published online in November 2006 with corrections to the Cover Date. |
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