Nonlinear Optical Properties and Ultrafast Carrier Dynamics of 2D Indium Selenide Nanosheets

This work reports the nonlinear optical properties and ultrafast carrier dynamics of indium selenide (InSe) nanosheets obtained via liquid-phase exfoliation under pulsed excitation with different durations. InSe nanosheets exhibit a better saturable absorption response under 6 ns pulse excitation than that under 380 fs excitation. In addition, the scattering phenomena of InSe dispersions with different mechanisms under various pulse durations are discovered, which are caused by the thermal effect under ns pulse excitation and dynamic spatial self-phase modulation affected by laser streaming under fs pulse excitation. The pump-probe measurements reveal that the InSe dispersion has ultrafast saturable absorption and photoinduced absorption processes, which may be caused by free carrier absorption or bandgap renormalization.