Whispering gallery mode micro-lasing in CsPbI₃ quantum dots coated on TiO₂ microspherical resonating cavities

Whispering gallery mode (WGM) lasing in CsPbI₃ quantum dots (QDs) coated on TiO₂ spherical microcavities is demonstrated. The photoluminescence emission from a CsPbI₃-QDs gain medium strongly couples with a 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 of magnitude 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 µm). 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.