Exciton–Polariton Effect and Polarized High-Quality Lasing in 1D CsPbBr₃-CsPb₂Br₅ Perovskite Planar Microcavities via Solution-Driven Soft Thermal Imprinting

High-quality laser modes (Q-factor of ≈6520) are achieved through the self-assembly of 1D metal halide perovskite (MHP) planar microwires (MWs) with a preferred orientation using a solution-driven soft thermal imprinting technique. The coexistence of CsPbBr₃ and CsPb₂Br₅ crystal phases within these MHP MWs, supported by well-matched heterointerfaces and improved resistance to environmental degradation, underpins their high exciton binding energy and the realization of exceptional laser quality factors in Fabry–Pérot (FP) resonators. Strong exciton-polariton coupling is demonstrated across various wire lengths, with Rabi splitting energies ranging from 145 to 180 meV, as revealed by a modified Lorentz oscillator model. This rapid increase in the group refractive index near the excitonic transition further exemplifies the energy-band dispersion inherent to exciton-polaritons. These novel structures, which function as microcavities, also yield waveguide modes that exhibit an exceptionally high degree of linear polarization. By leveraging these light-matter interactions and waveguide architectures, this work paves the way for cost-effective, solution-processed perovskite photonic devices with high-quality, linearly polarized lasing and optical nonlinearity applications.