The amplitude of self-oscillating mechanical resonators in cavity optomechanical systems is typically limited by nonlinearities arising from the cavity's finite optical bandwidth. We propose and demonstrate a feedback technique for increasing this limit. By modulating the cavity input field with a signal derived from its output intensity, we increase the amplitude of a self-oscillating GHz frequency mechanical resonator by 22% (increase in coherent phonon number of 50%) limited only by the achievable optomechanical cooperativity of the system. This technique will advance applications dependent on high dynamic mechanical stress, such as coherent spin-phonon coupling, as well as implementations of sensors based on self-oscillating resonators.
@article{arxiv.2308.09130,
title = {Feedback Enhanced Phonon Lasing of a Microwave Frequency Resonator},
author = {Peyman Parsa and Prasoon Kumar Shandilya and David P. Lake and Matthew E. Mitchell and Paul E. Barclay},
journal= {arXiv preprint arXiv:2308.09130},
year = {2023}
}