Transverse radiation force in a tailored optical fiber

TL;DR

This paper demonstrates that a slight azimuthal asymmetry in an optical fiber's refractive index can cause a measurable transverse radiation force, potentially useful for micron-scale fiber manipulation.

Contribution

It introduces a simple model showing how small refractive index differences induce transverse forces, linking theory to recent experiments and suggesting practical applications.

Findings

A small refractive index difference (~10^{-3}) causes a ~10 micron displacement.

The effect likely explains observations in recent experiments.

Potential for controlled bending of optical fibers for micro-devices.

Abstract

We show, by means of simple model calculations, how a weak laser beam sent through an optical fiber exerts a transverse radiation force if there is an azimuthal asymmetry present in the fiber such that one side has a slightly different refractive index than the other. The refractive index difference $\Delta n$ needs only to be very small, of order $10^{-3}$, in order to produce an appreciable transverse displacement of order 10 microns. We argue that the effect has probably already been seen in a recent experiment of She et al. [Phys. Rev. Lett. 101, 243601 (2008)], and we discuss correspondence between these observations and the theory presented. The effect could be used to bend optical fibers in a predictable and controlled manner and we propose that it could be useful for micron-scale devices.