Room temperature amplified spontaneous emission in CsPbBr3 polycrystalline thin films in transmission configuration

We present an experimental study concerning the interplay between amplified spontaneous emission (ASE) and photoluminescence in polycrystalline thin films (100–300 nm) realized by Radio-Frequency Magnetron Sputtering (RF-MS) without the use of a waveguide configuration. Our results show that the amplification of the spontaneous emission requires only a thickness comparable to the absorption length (≈100 nm). Moreover, the strong ASE signal measured at room temperature shows a peculiar behavior performing a z-scan of the exciting beam waist: increasing the fluence, the decrease of the ASE intensity is accompanied by a significant decrease of the absorption coefficient, indicating the onset of a non-linear process due to multiexciton population (space filling effect) in the film nanocrystallites. Our studies performed with high spectral resolution reveal a modal structure with a significant stability in time, both in the spectral line shape and intensity, from pulse to pulse and demonstrate that CsPbBr3 nanometric films deposited by RF-MS can be efficiently used as active material for coherent light amplification. Moreover, the absorption change detected at high photon fluence can be used for the development of light modulators.