We investigate self-organized synchronization in a blue-detuned optomechanical cavity that is mechanically coupled to an undriven mechanical resonator. By controlling the strength of the driving field, we engineer a mechanical gain that balances the losses of the undriven resonator. This gain-loss balance corresponds to the threshold where both coupled mechanical resonators enter simultaneously into self-sustained limit cycle oscillations regime. This leads to rich sets of collective dynamics such as in-phase and out-of-phase synchronizations, depending on the mechanical coupling rate, the frequency mismatch between the resonators, and the external driving strength through the mechanical gain and the optical spring effect. Moreover, we show that the introduction of a quadratic coupling, which results from a quadratically coupling of the optical cavity mode to the mechanical displacement, enhances the in-phase synchronization. This work shows how phonon transfer can optomechanically induce synchronization in a coupled mechanical resonator array and opens up new avenues for phonon processing and novel memories concepts.

• Received 28 July 2020
• Revised 31 August 2020
• Accepted 2 September 2020

DOI:https://doi.org/10.1103/PhysRevB.102.155410