Feedback Enhanced Phonon Lasing of a Microwave Frequency Resonator

TL;DR

This paper introduces a feedback method to enhance the amplitude of self-oscillating mechanical resonators in cavity optomechanics, achieving a 22% increase and enabling advanced applications like spin-phonon coupling and sensitive sensors.

Contribution

The paper presents a novel feedback technique that significantly increases the amplitude limit of GHz mechanical resonators in optomechanical systems.

Findings

Achieved a 22% increase in resonator amplitude.

Enhanced coherent phonon number by 50%.

Demonstrated the technique's potential for advanced sensing applications.

Abstract

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.