Coupling between guided modes of two parallel nanofibers

TL;DR

This paper analytically and numerically investigates the coupling of guided modes in two parallel nanofibers, revealing conditions for efficient power transfer and potential applications in metrology.

Contribution

It provides a detailed analysis of mode coupling coefficients considering fiber parameters, highlighting the system's potential for precise distance and wavelength measurements.

Findings

Mode coupling depends on fiber radius, wavelength, and separation.

Power transfer can be maximized or nullified by adjusting parameters.

System shows promise for nanometric distance and wavelength sensing.

Abstract

We study the coupling between the fundamental guided modes of two identical parallel nanofibers analytically and numerically. We calculate the coefficients of directional coupling, butt coupling, and mode energy changes as functions of the fiber radius, the light wavelength, and the fiber separation distance. We show that, due to the symmetry of the system, a mode of a nanofiber with the principal quasilinear polarization aligned along the radial or tangential axis is coupled only to the mode with the same corresponding principal polarization of the other nanofiber. We find that the effects of the butt coupling and the mode energy changes on the power transfer are significant when the fiber radius is small, the light wavelength is large, or the fiber separation distance is small. We show that the power transfer coefficient may achieve a local maximum or become zero when the fiber radius, the light wavelength, or the fiber separation distance varies indicating the system could be used in metrology for distance or wavelength measurements.