Whispering Gallery and Fabry‐Pérot Resonators for Photonics and Halide Perovskite Optoelectronics

ABSTRACT Halide perovskites, with their high refractive indices, strong excitonic interactions, and low optical losses, provide a unique platform for dielectric optical resonators. Among these, Whispering Gallery Mode (WGM) and Fabry–Pérot (FP) resonators enable light confinement through distinct yet complementary mechanisms based on total internal reflection and longitudinal interference. While both architectures have been widely explored in halide perovskite microlasers, optical sensors, and solar cells, their roles have largely been discussed in isolation. Here, we present a unified perspective on dielectric resonators in halide perovskite optoelectronics, identifying them as coherent, mode‐based light‐trapping systems. In contrast to conventional non‐resonant nanophotonic strategies that rely on scattering and geometric light management, WGM and FP resonators enhance optical path length, field localization, and photon lifetime through well‐defined cavity modes. This distinction underpins their performance in perovskite‐based low‐threshold lasing, high‐sensitivity sensing, and enhanced absorption in thin‐film photovoltaics, particularly near the band edge where photon recycling becomes critical. By systematically analyzing resonator implementations across these applications, we outline key design principles, performance trade‐offs, and integration challenges specific to halide perovskite platforms. Finally, we highlight the remaining challenges and emerging opportunities, including hybrid WGM–FP systems and resonator‐driven photon recycling for high‐efficiency perovskite devices.