We investigate the photorefractive properties of Sn<sub>2</sub>P<sub>2</sub>S<sub>6</sub> in the near infrared wavelength range. Conventional "yellow" and modi?ed "brown" crystals are examined, which were grown by vapor-transport technique using respectively SnI<sub>4</sub> and SnI<sub>2</sub> as a transporter agent. We measured an increase of the photorefractive gain from 3 cm<sup>-1</sup> in yellow samples to 18 cm<sup>-1</sup> in brown samples at 780 nm. Self-pumped phase conjugation was studied in a ring cavity scheme. Using yellow sample phase conjugate re?ectivity at 780 nm is about 55% and the response time in the order of 5 s at 20 mW. The phase-conjugate response in brown samples, however, is observed in only about 20 ms, which is two-orders of magnitude faster.
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