Synthetic cooling translational mode of an optically trapped nanoparticle through librational mode

TL;DR

This paper explores the nonlinear dynamics and multi-stability of an optically levitated nonspherical nanoparticle, demonstrating a synthetic cooling scheme for translational motion via librational mode coupling.

Contribution

It introduces a systematic analysis of multi-stability and nonlinear coupling in nanoparticle modes, proposing an optimized synthetic cooling method combining feedback and mode coupling.

Findings

Multi-stability occurs with red-detuned drives for librational or translational modes.

System stabilization requires both drives to be blue-detuned.

Synthetic cooling can be optimized by matching drive amplitudes and adjusting air pressure.

Abstract

We systematically investigate the multi-stability behaviour and cooling of both librational and translational modes of an optically levitated nonspherical nanoparticle. By expanding the trapping potential to the fourth order of both the translational and librational freedom degrees, we deduce the nonlinearity of them and their nonlinear coupling. Through stability analysis, we find that the system presents multi-stability when either the librational or the translational drive is red-detuned. The system will be stabilized if and only if these two drives are both blue-detuned. In the steady state region, we study the synthetic cooling scheme of translational mode by utilising librational mode. We find that matching the driving amplitude of these two modes and appropriate air pressure can optimize synthetic cooling. The synthetic cooling limit can be greatly improved, if we combine the feedback cooling with the synthetic cooling.