Subitan Laskar

Lead halide perovskites (LHPs) have garnered significant attention due to their exceptional optical and electronic properties. The tunable bandgaps and high absorption coefficients of LHPs enable the design of high-efficiency solar cells that can capture a broader spectrum of sunlight. Additionally, their excellent charge carrier mobility and solution-processability make them ideal for creating flexible and lightweight solar panels. In photodetectors, perovskite QDs offer high sensitivity and fast response times, making them suitable for applications in imaging, sensing, and communication technologies. Furthermore, LHPs high PLQY can be utilized to exhibit promising lasing behaviour, essential for developing advanced photonic devices. These properties make LHPs suitable for various optoelectronic applications, including solar cells, light-emitting diodes (LEDs), lasers, and photodetectors.

TiO2 microspheres encapsulated with photostable Cs0.5Rb0.5PbBr3 quantum dots (QDs) are shown to exhibit whispering gallery mode (WGM) microcavity lasing. Cs0.5Rb0.5PbBr3-QDs have high photostability and photoluminescence quantum yield (PLQY) compared to CsPbBr3 and CsPbI3 QDs. A strong synergy between TiO2 optical microcavity and the PL emission from Cs0.5Rb0.5PbBr3-QDs serving as the gain medium is evidenced from the WGM-less, spontaneous emission arising at a low excitation laser power transitioning to a stimulated lasing emission characteristics of WGM modes beyond the critical threshold of 7.98 kW/cm2. Upon excitation with an Ar-ion laser (λex = 488 nm), a substantial amplification exceeding an order of magnitude is observed at this threshold. The WGM lasing in this system exhibits a high-quality factor (Q) of ~1807 at room temperature. Remarkably, the WGM lasing maintains photostability, with no discernible photodegradation even under elevated continuous laser power of ~20.03 kW/cm2 for 90 minutes. WGM lasing is also observed in coupled doublet and triplet microspheres; however, the Q-factor decreases as the number of coupled microcavities increases. Rb-substituted halide QDs show potential for photostable, tuneable WGM microlaser applications.

Whispering gallery mode (WGM) lasing in CsPbI3 quantum dots (QDs) coated on TiO2 spherical microcavities is demonstrated. The photoluminescence emission from CsPbI3-QDs gain medium strongly couples with TiO2 microspherical resonating optical cavity. Spontaneous emission in these microcavities switches to a stimulated emission above a distinct threshold point of 708.7 W/cm2. Lasing intensity increases three to four times as the power density increases by one order beyond the threshold point when the microcavities are excited with a 632 nm laser. WGM microlasing with quality factors as high as Q~1195 is demonstrated at room temperature. Quality factors are found to be higher for smaller TiO2 microcavities (~2 mm). CsPbI3-QDs/TiO2 microcavities are also found to be photostable even after continuous laser excitation for 75 minutes. The CsPbI3-QDs/TiO2 microspheres are promising as WGM based tunable microlasers.