Exchange-Coupled Localized States Enable Weak-Field Spin-Polarized Lasing in All-Inorganic CsPbBr 3 Microcrystals

Spin-polarized lasers promise to transform photonic information processing by converting carrier spin angular momentum into circularly polarized photons. However, rapid spin relaxation in lead halide perovskites has hindered the realization of spin-polarized lasing. Here, we report weak-field spin-polarized lasing in Mn-doped all-inorganic CsPbBr 3 microcrystals by exploiting Mn-induced exchange-coupled localized-state dynamics. Spectroscopic measurements indicate that Mn doping introduces a shallow localized state coupled to the host band edge, enabling ultrafast carrier trapping and subsequent back-transfer. Under an external magnetic field, the Mn-related exchange interaction likely enhances spin retention and reduces spin depolarization, leading to a pronounced extension of the spin lifetime under a weak magnetic field. By integrating this weak-field-enhanced spin-retention pathway with whispering-gallery-mode resonators, we realize weak-field-controlled spin-polarized lasing at room temperature. At 300 mT, the Mn-doped microcrystals exhibit a 5-fold increase in spin lifetime to 16.6 ps, together with a low threshold of 3.05 μJ cm –2 and a degree of circular polarization of 39.6%.