Fig. 4: Characterizations of the CsPbBr₃ beam splitter.

Real-space PL images (a, c) and PL microscope image (b) of the perovskite beam splitter above the threshold (at 63 μJ cm⁻²). The white dashed circles and boxes depict the regions of excitation terminals and propagation terminals, respectively. The diameter of the excitation spots is about 10 μm. The dotted arrows represent the directions of lasing propagation. Scale bar: 3 μm. d, f Normalized PL spectra of the perovskite beam splitter with different excitation configurations and propagation directions corresponding to (a) and (c). The red, green and blue curves represent the PL emission detected at A, C, and D points, respectively. The propagation efficiencies T_AC and T_AD for excitation configuration (d) are 15.98% and 15.62%, and T_DA and T_DC for excitation configuration (f) are 4.50% and 1.38%, respectively. e ARPL spectra of the beam splitter detected at both C and D points simultaneously, exhibiting the coherence of lasing emission from the two arms of the beam splitter.