Intrinsic transverse spin angular momentum of fiber eigenmodes

TL;DR

This paper investigates the intrinsic transverse spin angular momentum of fiber eigenmodes, deriving analytical expressions and identifying optimal fiber parameters to maximize surface transverse spin, with implications for optical nanofiber applications.

Contribution

It provides the first analytical expressions for transverse spin angular momentum in fiber eigenmodes and identifies optimal fiber dimensions for maximum surface transverse spin.

Findings

Transverse spin angular momentum is significant in nanofibers and increases in the evanescent field.

Optimal fiber radius for maximum surface transverse spin is one-fourth of the wavelength.

Transverse spin induces mechanical effects on small particles near the fiber surface.

Abstract

We study the transverse spin angular momentum of fiber eigenmodes. As an intrinsic property of fiber eigenmodes, it becomes considerable in optical nanofibers and, especially, increases sharply in the evanescent field. We derive analytical expressions of this angular momentum, and present its density distribution inside andoutside nanofibers. Significantly, we find the optimal ratio of the fiber core radius to the wavelength to obtain the maximum surface transverse spin. For instance, the optimal fiber radius is one fourth of the wavelength for the fundamental mode. Furthermore, we investigate the spin flow of each guided mode on the nanofiber surface and the transverse mechanical effects originated from the transverse spin on small particles.