Fig. 1. Optical characterizations of perovskite CsPb2Br5 microplates. (a) SEM image. The scale bar is 10 μm. (b) Schematic crystal structure. (c) Experimental and standard powder XRD patterns of tetragonal CsPb2Br5. (d) Linear absorption (green) and PL spectrum (red).

Fig. 2. TA spectra of perovskite CsPb2Br5. (a) 2D pseudo-color TA spectra. (b) TA spectra at different delay times. (c) The kinetics of prominent PB signal. (d) The kinetics of SE. Inset: a magnified view of the spectroscopic signature of SE before 11 ps.

Fig. 3. Temperature-dependent ASE actions from CsPb2Br5 microplates. (a) The PL spectra of two-photon pumped ASE at 300 K. Inset: photograph of the CsPb2Br5 microplate excited above ASE threshold by a cylindrical lens. (b) The integrated intensity and FWHM with respect to pump intensity. (c) Normalized PL intensity as a function of excitation intensity at different temperatures. (d) Pump threshold intensity versus temperature. The solid red line is the fit according to Eq. (1).

Fig. 4. F-P mode lasing characterization of a single CsPb2Br5 microplate. (a) Pump-intensity-dependent emission spectra under two-photon excitation. Inset: the bright-field optical image and emission photograph from the single microplate above the lasing threshold, indicating the F-P mode. The scale bar is 5 μm. (b) Output intensity (blue) and FWHM (red) of laser with increasing pump fluence. (c) Fitting of the lasing oscillation mode. The FWHM is 0.15 nm with a quality factor of ∼3551.

Fig. 5. WGM lasing characterization of a single CsPb2Br5 microplate. (a) Pump-intensity-dependent emission spectra under two-photon excitation. Inset: the bright-field optical image and the emission photograph from the single CsPb2Br5 microplate above the lasing threshold, indicating the WGM lasing. The scale bar is 5 μm. (b) Output intensity (red) and FWHM (blue) of laser with increasing pump fluence. (c) Fitting of the lasing oscillation mode. The FWHM is 0.16 nm with a quality factor of ∼3374.

Fig. 6. Log–log plot of the integrated PL intensity as a function of the pump fluence under two-photon excitation.

Fig. 7. Pump-intensity-dependent SE dynamics.

Fig. 8. Normalized integrated intensity for microplates under pulsed excitation.

Fig. 9. Two-photon pumped intensity-dependent emission spectra from a single CsPb2Br5 microplate in the F-P cavity.

Fig. 10. Center lasing position of the CsPb2Br5 F-P mode laser.

Fig. 11. Two-photon pumped intensity-dependent emission spectra from a single CsPb2Br5 microplate in the WGM cavity.

Fig. 12. Center lasing position of the CsPb2Br5 WGM laser.