Nonlinear optical properties of GaAs/(AlGa)XOY heterostructures using interband excitation by 150 fs laser pulses is
reported. A considerable wideband nonlinear response is observed. Mean decay time for nonlinear reflection in
heterostructures ranges from 1.5 to 3.5 ps. The shift of the GaAs energy-band structure caused by the high tensions in
GaAs/(AlGa)XOY structure is observed.
ZnS/ZnSe heterostructures under condition of ZnSe interband excitation by a 150 fs laser pulse exhibit strong narrow-band
modification of absorption and wide-band modification of reflection. Mean decay time for nonlinear reflection in
heterostructures ranges from 2 to 3 ps whereas in bare ZnSe monolayer it exceeds 5 ps. Possible physical processes
responsible for nonlinear refraction in the transparency region include interplay of absorption driven nonlinear refraction
via Kramers-Kronig relations and intrinsic dielectric properties of dense electron-hole plasma. For nonlinear absorption
at ZnSe band edge, interplay of plasma screening effects and states filling effects are relevant.
ZnS/ZnSe Bragg reflectors under condition of ZnSe interband excitation by a femtosecond laser pulse exhibit strong
narrow-band modification of absorption and wide-band modification of reflection. Mean decay time for nonlinear
reflection in heterostructures ranges from 2 to 3 ps whereas in bare ZnSe monolayer it exceeds 5 ps. Possible underlying
physical processes responsible for nonlinear refraction in the transparency region include interplay of absorption driven
nonlinear refraction via Kramers-Kronig relations and intrinsic dielectric properties of dense electron-hole plasma. For
nonlinear absorption at ZnSe band edge, interplay of plasma screening effects and states filling effects are relevant.
Nonlinear optical response of periodic structures based on ZnSe/ZnS heterostructures using interband excitation of a ZnSe sublattice by 1 50 fs laser pulses is reported. A considerable shift of reflection spectrum and large relative reflection changes were observed in a wide spectral range corresponding to the transparency region of ZnSe far from the intrinsic absorption onset. Evaluated refraction index change is about -0.02 with the relaxation time being about 3 picoseconds. The nonlinear refraction is supposed to be controlled by population induced absorption changes in ZnSe single crystals and relevant refraction index modification via Kramers-Kronig relations. The nonlinearity relaxation time is supposed to trace a transition from non-equilibrium to quasi-equilibrium distribution of electrons and holes within ZnSe conduction and valence bands, respectively, rather than electron-hole recombination time. The nonlinearity
mechanism does not reduce to just population dependent absorption saturation but essentially results from the specific distribution function in the first instance after excitation.
We investigated ultrafast nonlinear optical properties of periodic structures based on ZnSe/ZnS using interband and two-photon excitation of ZnSe sublatice by nano-, pico-, and femtosecond laser pulses. A considerable shift of reflection spectrum and large relative reflection changes were observed in a wide spectral range corresponding to the transparency region of ZnSe far from the intrinsic absorption onset. The nonlinear refraction is supposed to be controlled by population induced absorption changes in ZnSe and the relaxation time is controlled by a transition from non-equilibrium to quasi-equilibrium distribution of electrons and holes.
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