Enhanced photorefractive properties of tin hypothiodiphosphate ( Sn 2 P 2 S 6 ) crystals as a result of Bi doping are presented. These new crystals were obtained by the vapor-transport technique using stoichiometric Sn 2 P 2 S 6 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 ∼ 750 nm and shift toward the red wavelengths with increasing Bi concentration. Sn 2 P 2 S 6 : 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 (i) pure Sn 2 P 2 S 6 ( 2.5 cm − 1 at 854 nm ), (ii) Sn 2 P 2 S 6 crystals modified by the growth conditions ( 14 cm − 1 at 860 nm ), and (iii) Te-doped Sn 2 P 2 S 6 ( 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 Λ = 9.8 and 1.3 μ m , respectively, are found; Bi-doped Sn 2 P 2 S 6 crystals are the fastest among all the presently known Sn 2 P 2 S 6 crystals operating at near-infrared wavelengths.