Long-range optical trapping and binding of microparticles in hollow-core photonic crystal fibre

TL;DR

This paper demonstrates long-range optical binding of microparticles within a hollow-core photonic crystal fibre, enabling stable particle arrays and mechanical mode observations over centimeter scales in an isolated environment.

Contribution

It reports the first observation of stable long-range optical binding of microparticles inside HC-PCF, supported by a new analytical model of their dynamics.

Findings

Particles bound at ~40 μm distance, 50 times the laser wavelength.

Array can be translated over centimeters along the fibre.

Mechanical modes observed at low gas pressure.

Abstract

Optically levitated micro- and nanoparticles offer an ideal playground for investigating photon-phonon interactions over macroscopic distances. Here we report the observation of long-range optical binding of multiple microparticles, mediated by intermodal scattering and interference inside the evacuated core of a hollow-core photonic crystal fibre (HC-PCF). Three polystyrene particles with 1 {\mu}m diameter are stably bound together with an inter-particle distance of ~40 {\mu}m, or 50 times longer than the wavelength of the trapping laser. The bound-particle array can be translated to-and-fro over centimetre distances along the fibre. When evacuated to 6 mbar gas pressure, the collective mechanical modes of the bound-particle array could be observed. The measured inter-particle distance at equilibrium and mechanical eigen-frequencies are supported by a novel analytical formalism modelling the dynamics of the binding process. The HC-PCF system offers a unique platform for investigating the rich optomechanical dynamics of arrays of levitated particles in a well-isolated and protected environment.