Abstract

We present data on the enhanced photorefractive properties of Sn<sub>2</sub>P<sub>2</sub>S<sub>6</sub> as a result of doping by Te. These new crystals were obtained by vapor-transport technique using stoichiometric Sn<sub>2</sub>P<sub>2</sub>S<sub>6</sub> composition with an additional amount of Te up to 3 mol. % in the initial compound. The optical absorption spectra of the grown crystals contain an additional band located near the fundamental absorption edge, which increases with the Te concentration. Sn<sub>2</sub>P<sub>2</sub>S<sub>6</sub>:Te crystals are found to exhibit larger two-beam coupling gain coefficients <i>Γ</i> (up to 12 cm<sup>-1</sup> at a wavelength of 633 nm and up to 7 cm<sup>-1</sup> at 780 nm) as compared to pure Sn<sub>2</sub>P<sub>2</sub>S<sub>6</sub> (4-7 cm<sup>-1</sup> at 633 nm and 2.5 cm<sup>-1</sup> at 780 nm). Additionally, the grating build-up becomes faster in comparison with both, nominally pure yellow and brown Sn<sub>2</sub>P<sub>2</sub>S<sub>6</sub> modified by the growth conditions. The typical time response is 2-5 msec for He-Ne laser irradiation with an average intensity <i>I</i> = 0.3 W·cm<sup>-2</sup>. The results on a self-pumped ring-loop beam oscillator based on such Te-doped Sn<sup>2</sup>P<sup>2</sup>S<sup>6</sup> crystals studied at 633 and 780 nm show the reflectivity close to its theoretical limit and fast rise time of the conjugated beams.

© 2003 Optical Society of America

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