Precise Control of Single‐Crystal Perovskite Nanolasers

Efficient control of integrated light sources is crucial to advancing practical applications of nanophotonics. Despite the success of microlasers, their sophisticated nanostructures are not applicable in nanolasers. The situation for bottom-up-synthesized nanolasers becomes more challenging due to the constraints of fixed cavity shapes and fragile material stability. Here, the physics of exceptional points (EPs) is employed, and a strategy is demonstrated to precisely tune the lasing actions in lead halide perovskite nanorods. By placing a nanoparticle to the boundary of a square nanocavity, it is shown that EPs regularly and controllably emerge as a function of the nanoparticle position. Consequently, both the internal lasing actions and their far-field radiation can be completely reversed with a tiny displacement of <100 nm. The new strategy for controlling lasing actions in nanocavities is confirmed with numerical simulations and lasing experiments. This research can also bring new avenues for ultrasensitive position sensing.