Whispering gallery mode lasing in lead halide perovskite crystals grown in microcapillary

Microcapillaries enable us to simply prepare crystalline perovskites in a microcavity. A precursor solution of methyl ammonium lead bromide (CH3NH3PbBr3) is injected by capillary action into quartz microcapillaries with an inner diameter (ϕ) of 2–40 μm. After drying at 70 °C in the atmosphere, cylindrical crystals are precipitated to fill up the inner cavity of the microcapillary. Under optical pumping, whispering gallery mode lasing depending on ϕ is observed. With reducing ϕ, the mode number and the lasing threshold fluence are found to be decreased. This suggests that the stimulated emission can be enhanced by cavity quantum electrodynamics in CH3NH3PbBr3 crystals which are densely confined in the microcavity. Consequently, the microcapillary with ϕ = 2 μm realizes single-mode lasing at a threshold fluence of 4.7 μJ/cm2.