Self-Injection Locking for Low Phase Noise Phonon Laser

Phonon lasers, as analogues of optical lasers, have received widespread attention in optomechanical systems. In this Article, we achieve phonon laser self-injection locking using a microwave photonic architecture with a feedback loop, which can be analyzed as an optoelectronic cavity. The line width of the phonon laser with mechanical frequency of 4.97 GHz is narrowed from 3 kHz to 150 Hz at room temperature. The phase noise of the phonon laser can be as low as -95 dBc/Hz at a frequency offset of 10 kHz, representing a decrease of 40 dB compared to the free-running state. Additionally, we lock two phonon lasers onto different cavity modes within the same fiber loop, achieving a parallel output of the phonon lasers. This research yields promising results in the development of a low-noise oscillator, a coherent phonon laser, and mode-locked phonon lasers in optomechanical arrays.