Tunable nonlinear absorption effect and carrier dynamics of perovskite quantum dots

The nonlinear optical absorption effects of perovskite quantum dots (QDs) in nanosecond and femtosecond regimes are studied. By tuning the absorption edge via adjusting the halogen elements in the perovskite QDs, the materials could exhibit excellent saturable absorption (SA) effects, both for 400 nm femtosecond laser-pulses and 532 nm nanosecond laser-pulses. Femtosecond transient absorption spectroscopy measurements reveal that photoinduced bleaching of the valance band and filling of the conduction band was responsible for the strong SA effect of the QDs. The ultra-low SA intensity of the QDs indicates that the materials have important application potential in mode-locking and Q-switched lasers.