Fig. 1. Schematic diagram and mechanism of polariton parametric oscillator in the perovskite microcavity. (a) Microscopy image and fluorescence microscopy image of the CsPbBr3 perovskite single crystal. (b) Experimental geometry of the CsPbBr3 perovskite microcavity, in which a thick CsPbBr3 perovskite is sandwiched by two DBRs. (c) Angle-resolved photoluminescence spectrum of CsPbBr3 microcavity along H polarization under CW excitations. The dashed black line displays the theoretical fitting dispersion of the LP dispersion; the solid black lines show the dispersions of uncoupled CsPbBr3 perovskite exciton (X) and cavity photon mode (C); the detuning Δ is indicated in this figure. (d) Hopfield coefficients illustrating the exciton (XLP) and photon (CLP) fraction of the LP dispersion along x polarization; the blue vertical line denotes the signal state polariton (ks); the green vertical line represents the pump state polariton (kp).

Fig. 2. Observation and characterizations of polariton oscillation at room temperature. Experimental far-field emission of (a) energy–kx and (b) kx-ky at the pump power of 0.5Pth. Experimental far-field emission of (c) energy–kx and (d) kx-ky at the pump power of 3Pth. Theoretically calculated far-field emission of (e) energy–kx and (f) kx-ky at the pump power of 0.5Pth. Theoretically calculated far-field emission of (g) energy–kx and (h) kx-ky at the pump power of 3Pth. (i) Signal-state ks emission intensity as a function of pump kp fluence in a log–log scale, demonstrating a super-linear increase by three orders of magnitude near threshold. (j) Signal-state ks emission linewidth as a function of pump kp fluence along with a sharp narrowing linewidth from 12 to 2 meV at the threshold. (k) Signal-state ks emission peak energy with a continuous blueshift trend.

Fig. 3. Characterizations of polariton oscillator versus pump states for three samples with different detunings Δ=−50, −82, −100meV, respectively. (a)–(c) The pump state is tuned with energy and angle to resonantly excite the LP dispersion for detunings (a) Δ=−50meV, (b) Δ=−82meV, and (c) Δ=−100meV. (d)–(f) The energy conversion threshold as a function of pump state angle for detunings (d) Δ=−50meV, (e) Δ=−82meV, and (f) Δ=−100meV. The lowest energy conversion threshold peaks at (d) Pth=0.3μW, (e) Pth=0.8μW, and (f) Pth=2.5μW, respectively. The black circles denote the occurrence of OPO, whereas the red circles represent cases where the OPO was not present.

Fig. 4. Polarization dependence of the polariton parametric oscillator. (a) Angle-resolved photoluminescence spectrum of CsPbBr3 microcavity along V polarization and H polarization under CW excitation. (b) Polar plot of the H polarized pump excited at Ep=2.326eV (533 nm), centered kx=6.8μm−1 (black circle dots), and fitting function (black solid line) f∝cos2θ. (c) Under excitation of (b), polar plot of the measured polarization emission of the signal state at EsH=2.287eV, kx=0μm−1 (red circle dots) and fitting function (red solid line) f∝cos2θ. (d) Polar plot of the left circularly polarized pump excited at Ep=2.326eV (533 nm), centered kx=6.8μm−1 (black circle dots), as well as a fitting constant function (continuous line). (e) Under excitation of (d), polar plot of the measured polarization emission of the signal state at EsH=2.287eV, kx=0μm−1 (red circle dots), and fitting function (red solid line) f∝cos2θ; at EsV=2.296eV, kx=0μm−1 (blue circle dots), and fitting function (blue solid line) f∝cos2(θ+90deg).