Application of Z-scan technique for the study of nonlinear absorption in chemically reduced LiNbO 3 crystals

International audienceBulk wave excitation from the surface of a LiNbO3 crystal by a system of planar electrodes A V Muromets, V B Voloshinov and I A Kanonin Investigation of the nonlinear absorption of [M(Et2timdt)2] (M = Pd, Pt) in the pico-andnanosecond timescales using the Z-scan technique T Cassano, R Tommasi, M Arca et al. Green synthesis and third-order nonlinear optical properties of 6-(9H-carbazol-9-yl) hexyl acetate Abstract. The nonlinear absorption (NLA) was studied by open-aperture Z-scan experiments in the chemically reduced nominally pure LiNbO 3 crystals at cw-illumination with the red (644 nm) and green (514.5 nm) laser beams. The magnitude of the measured NLA is considerably different from the reported Z-scan results obtained in as-grown LiNbO 3. The positive sign of NLA obtained with the red light has been related to the generation of the small bound polarons absorbing in red and near-IR ranges. Application of green light results in the light-induced transparency, i.e. the Z-scan traces show negative sign of NLA. Intensity dependence of Z-scan traces allows for conclusion that the photo-induced dissociation of small Nb Li 4+ :Nb Nb 4+ bipolarons and sequent generation of small polarons gives the dominating contribution to the nonlinear optical absorption in reduced crystals with a large bipolarons concentration