Lasing from reduced dimensional perovskite microplatelets: Fabry-Pérot or whispering-gallery-mode?

Room temperature amplified spontaneous emissions in a sub-centimeter sized CsPbBr3 bulk single crystal

All inorganic perovskite CsPbBr3 shows great potential in laser device because of its excellent luminescence characteristics, while the room temperature amplified spontaneous emission (ASE) in a large size CsPbBr3 bulk single crystal is still quite difficult. Herein, we have obtained the room temperature ASE in a sub-centimeter size CsPbBr3 bulk single crystal pumped with the single-photon excitation. Based on the reproducible light path within the CsPbBr3 bulk single crystal, the photonic feedback between the bottom and top facets naturally enhances the population inversion, which exhibits an amplified spontaneous emission threshold of ∼320 µJ/cm2. The blue shift of the ASE peak along with the increased pumping intensity is also observed and ascribed to the reduction of the refractive index and the energy band filling effect. These findings demonstrate the sub-centimeter size CsPbBr3 bulk single crystal to be an excellent candidate as an optical gain media for crystal lasers.

The Dissociation of Exciton During the Lasing of a Single CsPbBr3 Microplate

In this work, the lasing of a single CsPbBr₃ microplate (MP) fabricated with chemical vapor deposition (CVD) is investigated from the viewpoint of exciton dissociation characterized with steady-state photoluminescence (PL) and time-resolved photoluminescence (TRPL). It is confirmed that the lasing performance is disturbed by the dissociation of excitons. The increase of lasing threshold with temperature originates from the dissociation of free excitons (FEs) to localized carriers (LCs), and the lasing failure is mostly ascribed to the dissociation of FEs to free carriers (FCs). The working temperature of micro/nanolasers based on metal halide perovskites (MHPs) could be raised up to the temperature determined by exciton binding energy while the laser heating effect is dealt with well. These findings advance our understanding on the photophysics of the lasing behaviors of micro/nanocavities based on MHPs and help us promote their performance by having better thermal management.

Role of the Exciton-Polariton in a Continuous-Wave Optically Pumped CsPbBr3 Perovskite Laser

Lead halide perovskites have emerged as excellent optical gain materials for solution-processable and flexible lasers. Recently, continuous-wave (CW) optically driven lasing was established in perovskite crystals; however, the mechanism of low-threshold operation is still disputed. In this study, CW-pumped lasing from one-dimensional CsPbBr₃ nanoribbons (NBs) with a threshold of ∼130 W cm^-2 is demonstrated, which can be ascribed to the large refractive index induced by the exciton-polariton (EP) effect. Increasing the temperature reduces the exciton fraction of EPs, which decreases the group and phase refractive indices and inhibits lasing above 100 K. Thermal management, including reducing the NB height to ∼120 ± 60 nm and adopting a high-thermal-conductivity sink, e.g., sapphire, is critical for CW-driven lasing, even at cryogenic temperatures. These results reveal the nature of ultralow-threshold lasing with CsPbBr₃ and provide insights into the construction of room-temperature CW and electrically driven perovskite macro/microlasers.