ABSTRACT Molecular cavity optomechanics (COM) leverages ultrastrong interactions between confined optical fields and high‐frequency molecular vibration, providing a unique platform for exploring high‐frequency phonon dynamics. In this work, we theoretically propose the use of a hybrid molecular COM system for realizing an ultra‐low‐threshold mid‐infrared (MIR) phonon laser. Despite an optical quality factor of only , an ultra‐low threshold power of is achieved, enabled by giant single‐photon optomechanical coupling and molecular collective effect. Moreover, the mechanical gain and threshold power can be further tuned by adjusting the distance between mirrors of the Fabry‐Pérot cavity. Our findings establish the first direct connection between molecular COM and MIR phonon lasers, with potential applications in MIR acoustics and biomedical imaging.
Yin et al. (Sun,) studied this question.