Tin hypothiodiphosphate: nonlinear response in the sub-100 fs time domain

摘要: The interaction of sub-100 fs light pulses (τp ≲ 75 fs) with single crystals nominally undoped tin hypothiodiphosphate, Sn2P2S6, is studied in the near-infrared spectral range (590 – 1630 nm). A predominant contribution two-photon absorption (TPA) verified measurements sample transmission as a function pulse intensity and time delay between pump probe pulses. Scans over photon energy show that coefficient β increases superlinear way for energies hω exceeding Eg/2; any quantum it nearly independent propagation direction polarization incident beam. Such behavior qualitatively similar to predicted by perturbation theory within models allowed-forbidden transitions. TPA saturates at maximum value ≈ 8 cm GW−1 1.80 eV. It drops when reaching bandgap Eg. Using pump-probe 626 nm, transient persists delays much longer than duration, up 2.5 ns. We discuss our results framework microscopic structure Sn2P2S6 emphasis on optical generation S− small hole polarons.