Superfluorescence and nonlinear optical response of CH₃NH₃PbBr₃-based mesostructures: applications to amplified spontaneous emission and ultrafast lasers

Metal halide perovskites have unique luminescent properties that make them an attractive alternative for high quality light-emitting devices. However, the poor stability of perovskites with many defects and the long cycle time for the preparation of perovskite nanocomposites have hindered their production and application. Here, we prepared the perovskite mesostructures by embedding MAPbBr₃ nanocrystals in the mesopores on the surface of silica nanospheres and mixing the nanospheres with silver nanowires and poly(methyl methacrylate) (PMMA), and further explored their optical properties. The perovskite mesostructures exhibited superfluorescence (SF) under 785 nm laser excitation and the decay time was as short as 0.59 ps using a double exponential decay fit. The optical nonlinearity of these perovskite mesostructures under two-photon excitation was investigated by the Z-scanning technique. The samples exhibited both two-photon absorption (TPA) and saturation absorption (SA) with nonlinear absorption coefficients <i>β</i> ranging approximately 0.15 to 0.89 cm/GW corresponding to the TPA, and a saturation intensity of about 0.026 GW/cm² was determined. In addition, the quality of the perovskite mesostructures was shown to be significantly improved, including an increase in radiative efficiency and an extension of the optical gain lifetime. The samples were excited by a two-photon femtosecond laser pump at room temperature and atmospheric pressure, and the laser peak appeared at 540.1 nm with a low amplified spontaneous emission (ASE) threshold of 0.52 mJ/cm². Moreover, the perovskite mesostructures have been added to the fiber laser system as a saturable absorber, and the Q-switched pulse is generated at the wavelength of 1.5 µm. Our work effectively demonstrates that perovskite mesostructured materials can be functionalized for photonic devices, paving the way for further exploration of complex, functional and practical perovskite.