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

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Abstract
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.

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