Optomechanical Effects Occurring in a Hybrid Metal–Halide Perovskite Single Crystal Based on Photoinduced Resonant Ultrasound Spectroscopy

This letter reports optomechanical effects occurring in a hybrid metal-halide perovskite single crystal (MAPbBr3) based on resonant ultrasound spectroscopy (RUS) measurements under continuous wave (CW) laser illumination. The optomechanical effects are a new phenomenon in hybrid perovskite single crystals where the elastic constant of a single crystal is measured by RUS probed under varying excitation conditions. Our studies show that applying a CW laser (405 nm) to the single-crystal face shifts the RUS peaks to higher frequencies by about 1–4% in the perovskite single crystal at room temperature. The light-induced shift of the RUS peaks can be observed only when photoexcitation is occurring, rather than during heating, by positioning the laser wavelength within the optical absorption spectrum. In contrast, positioning the laser wavelength outside of the optical absorption spectrum leads to an absence of RUS peak shifting. Clearly, the laser-light-induced RUS peak shifts shows that the crystal elastic moduli can be changed by photoexcitation, leading to an optomechanical phenomenon via excited states. Essentially, the observed optomechanical phenomenon reflects the fact that the mechanical properties can be optically changed through internal repulsive and attractive force constants by external photoexcitation in a hybrid perovskite single crystal.