Fig. 3: Spatial and temporal coherence of BIC polariton condensate.
From: Exciton polariton condensation from bound states in the continuum at room temperature
a Top, interference patterns of BIC polariton condensates in a typical CsPbBr3 PhC lattice after the superposition of two mirror-symmetric images by the Michelson interferometer. Bottom, line profile of the coherence intensity extracted from the interference pattern (along y = 0). b Interference patterns (the dashed region in a) acquired at different time delays (Δt) of 0, 0.5, and 1.5 ps (denoted as P1, P2, and P3), respectively. The emission intensity at Δt = 0 was normalized for clarity. c Visibility of interference fringe as a function of delay time for BIC polariton condensation (purple) and the photonic lasing (orange). The visibility is obtained from time-dependent coherence fringes through the Fourier transform and fitted with the Gaussian function. Coherence times of 2.14 ps and 0.31 ps could be obtained for the BIC polariton condensation and the referenced pump laser, respectively. The yellow stars correspond to the three situations (P1, P2, and P3) in b. d Coherence time as a function of the pump density. The dots are taken from the measured temporal coherence for each value of pump density. The fitting line is calculated from power-dependent temporal coherence with an exponential function. The decrease in coherence time with increasing pump density is attributed to polariton–polariton scattering, which induces phase decoherence within the polariton lasing mode.
