Chiral Exciton‐Polariton Continuous‐Wave Perovskite Laser

Chiral optical materials offer a route to generate circularly polarized laser emission for spin-selective photonics, but realizing continuous-wave (CW) circularly polarized lasing at room temperature has remained challenging. Here, a chiral exciton-polariton CW laser is demonstrated using a microcavity strongly coupled with chiral 2D perovskite, (MBA)₂PbI₄. The resulting hybrid exciton-polaritons undergo lasing with ultralow threshold at an onset CW pump intensity of 0.5 W·cm^-2 at room temperature, orders of magnitude lower than all chiral halide perovskite lasers. The laser emission is intrinsically circularly polarized, with a luminescence dissymmetry factor (g_lum) about 0.30. Spectral tunability of the lasing wavelength is further demonstrated by adjusting the cavity thickness. The chiral polariton laser exhibits excellent stability under continuous operation, maintaining >95% of its output intensity over hours of CW pumping. The device represents a versatile platform with potential for spin-optoelectronic applications and for exploring spin-polarized quantum fluids of light at room temperature.