Self-diffraction from two-photon absorption gratings in Sn2P2S6.

Self-diffraction with the appearance of higher diffraction orders is discovered when writing a grating with a single sub-100 fs pulse in a nominally undoped Sn(2)P(2)S(6) sample. The short time of grating development, dependence of diffraction efficiency on the recording light intensity, correlation of wavelength dependence of efficiency with the spectrum of the two-photon absorption (TPA) constant, and a π phase shift of the diffracted beam allow for attributing the recorded grating to a dynamic amplitude grating of TPA.