Out-of-equilibrium optomechanical resonance self-excitation

TL;DR

This paper explores how increasing laser power in optomechanical systems can induce nonlinear effects that significantly enhance the effective quality factor of cantilevers, leading to out-of-equilibrium noise and self-oscillation.

Contribution

It demonstrates the nonlinear tuning of laser power to control the effective quality factor and noise in optomechanical resonances, advancing understanding of self-oscillation regimes.

Findings

Laser power tuning induces nonlinear optomechanical effects.

Effective quality factor can be dramatically increased.

Out-of-equilibrium noise is influenced by nonlinear damping.

Abstract

The fundamental sensitivity limit of atomic force microscopy is strongly correlated to the thermal noise of the cantilever oscillation. A method to suppress this unwanted noise is to reduce the bandwidth of the measurement, but this approach is limited by the speed of the measurement and the width of the cantilever resonance, commonly defined through the quality factor Q. However, it has been shown that optomechanical resonances in interferometers might affect the cantilever oscillations resulting in an effective quality factor Q$_{eff}$ . When the laser power is sufficiently increased the cantilever oscillations might even reach the regime of self-oscillation. In this self-oscillation state, the noise of the system is partially determined by the interaction with the laser light far from equilibrium. Here, we show and discuss how tuning of the laser power leads to nonlinear optomechanical effects that can dramatically increase the effective quality factor of the cantilever leading to out-of-equilibrium noise. We model the effects using a fourth order nonlinearity of the damping coefficient.