Halide perovskites are a promising optical gain medium with high tunability and simple solution synthesis. In this study, two gain regimes, namely, amplified spontaneous emission and random lasing, are demonstrated in the same MAPbBr3 halide perovskite single crystal. For this, photoluminescence is measured at a temperature of 4 K with pulsed femtosecond pumping by UV light with an 80 MHz repetition rate. Random lasing is observed in areas of the sample where a random resonator is formed due to cracks and crystal imperfections. In more homogeneous regions of the sample, the dominant regime is amplified spontaneous emission. These two regimes are reliably distinguished by the line width, the mode structure, the growth of the intensity after the threshold, and the degree of polarization of the radiation. The spectral localization of the stimulated emission well below the bound exciton resonance raises a question concerning the origin of the emission in halide perovskite lasers.
Halide perovskites are a family of materials with a high potential for realization of microlasers, due to their high luminescence quantum yield and broad spectral tunability. We demonstrate a single-step process for lasing microdisk fabrication from a thin film of methylammonium lead iodide (MAPbI3) perovskite through its patterning with tightly focused femtosecond (fs) laser pulses. By using kHz-scale pulse bursts destructive overheating of the material was suppressed. Perovskite microdisks fabricated under such optimized conditions showed stable lasing upon pumping with fs-laser both at lower (50 kHz) and higher (80 MHz) repetition rates and operation temperatures of 300 K and 6 K, respectively.
The MAPbI3 halide perovskite single crystals are studied at 5 K temperature using the photoluminescence excitation spectroscopy. Two noninteracting types of states are determined: bound excitons and defect‐related states. Excitation of the crystal with light energy below the bound exciton resonance reveals the complex low‐density defect emission, otherwise hidden by the emission of bound excitons. A way to separate these defect‐related luminescence spectra is proposed, and the thorough study of this emission regime is carried out. The results of this study open an area of low‐density defect and dopant exploration in halide perovskite semiconductors.
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