Spin-optomechanical coupling between light and a nanofiber torsional mode

TL;DR

This paper demonstrates the resonant driving of torsional mechanical modes in a nanofiber using polarized light, highlighting potential for quantum spin-optomechanics applications.

Contribution

It introduces a method to selectively excite nanofiber torsional modes via light polarization, advancing optomechanical control at the nanoscale.

Findings

Resonant amplification of torsional modes exceeds 35 dB.

Largest amplification occurs with light carrying longitudinal spin.

Nanofiber torsional modes have narrow resonances with Q≈2000.

Abstract

Light that carries linear or angular momentum can interact with a mechanical object giving rise to optomechanical effects. In particular, a photon transfers its intrinsic angular momentum to an object when the object either absorbs the photon or changes the photon polarization, as in an action/reaction force pair. Here, we present the implementation of light-induced selective resonant driving of the torsional mechanical modes of a single-mode tapered optical nanofiber. The nanofiber torsional mode spectrum is characterized by polarimetry, showing narrow natural resonances (Q$\approx$2,000). By sending amplitude modulated light through the nanofiber, we resonantly drive individual torsional modes as a function of the light polarization. By varying the input polarization to the fiber, we find the largest amplification of a mechanical oscillation (>35 dB) is observed when driving the system with light containing longitudinal spin on the nanofiber waist. These results present optical nanofibers as a platform suitable for quantum spin-optomechanics experiments.