Dynamic Control of Momentum‐Polarization Photoluminescence States with Liquid‐Crystal‐Tuned Nanocavities

Abstract Dynamic control of light, and in particular beam steering, is pivotal in various optical applications, including telecommunications, LiDAR, and biomedical imaging. Traditional approaches achieve this by interfacing a tunable modulating device with an external light source, facing challenges in achieving compact devices. Here, a dynamic photoluminescence (PL) modulating device is introduced, with which the properties of light directly emitted by a quasi‐2D perovskite (in particular, its directionality and polarization) can be modified continuously and over a large range. The device is based on a liquid‐crystal‐tunable Fabry‐Perot (FP) nanocavity and uses the FP energy‐momentum dispersion and spin‐orbit coupling between the excitons and the cavity modes to enable this dynamic control over the emitted radiation. With this device, electrically‐controlled, continuous, and variable emission angles are achieved up to a maximum of 28°, as well as manipulation of the PL polarization state, enabling both the creation of polarization gradients and the achievement of angle‐specific polarization conversion. Moreover, due to its resonant character, a threefold increase in the emission intensity is observed. This approach leverages the unique properties of actively tunable birefringent nanocavities to improve emission directivity, angle tunability, and polarization control, presenting a promising solution for next‐generation, deeply integrated beam steering devices.