Enhanced photorefractive properties of bi-doped Sn2P2S6

Enhanced photorefractive properties of tin hypothiodiphosphate (Sn2P2S6) crystals as a result of Bi doping are presented. These new crystals were obtained by the vapor-transport technique using stoichiometric Sn2P2S6 composition with an additional amount of Bi up to 0.5 mol. % in the initial compound. The bandgap, edges of the obtained crystals are located at similar to 750 nm and shift toward the red wavelengths with increasing Bi concentration. Sn2P2S6: Bi crystals are found to exhibit larger two-beam coupling gain coefficients (up to 17 cm(-1) at a wavelength of 854 nm) as compared to W pure Sn2P2S6 (2.5 cm(-1) at 854 nm), (ii) Sn2P2S6 crystals modified by the growth conditions (14 cm-1 at 860 rim), and (iii) Te-doped Sn2P2S6 (8 cm(-1) at 860 nm). At the same time, for an intensity of 1.3 W/cm(2) at 854 nm, buildup times of 0.9 and 2.5 ms at grating spacings of Lambda=9.8 and 1.3 gm, respectively, are found; Bi-doped Sn2P2S6 crystals are the fastest among all the presently known Sn2P2S6 crystals operating at near-infrared wavelengths. (c) 2008 Optical Society of America.