Femtosecond induced third-order optical nonlinearity in quasi 2D Ruddlesden-Popper perovskite film deciphered using Z-scan

Ruddlesden-Popper perovskite is a class of layered halide perovskite which gained much attention over the past few years in the field of photovoltaics. Herein, we have presented a compendious sketch of third-order nonlinear optical (NLO) properties of (PEA)₂Cs₄Pb₅Br₁₆, a quasi-two-dimensional (2D) perovskite using femtosecond Z-scan technique at 800 nm. Our open aperture (OA) Z-scan measurements unveiled saturable absorption (SA) behaviour of the 2D perovskite with a nonlinear absorption coefficient of −13.83 cm GW⁻¹, which is an order of magnitude higher than other 2D materials. Nonetheless, the self-defocusing effect has been demonstrated using a closed aperture (CA) Z-scan measurement. High nonlinear absorption coefficient and low saturation intensity (38.81 GW cm⁻²) infer that (PEA)₂Cs₄Pb₅Br₁₆ perovskite film could be useful for ultrafast photonic applications.