Transmittance and near-field characterization of sub-wavelength tapered optical fibers

TL;DR

This paper presents the fabrication and detailed analysis of sub-wavelength tapered optical fibers, enabling precise control of mode coupling and cutoff for whispering gallery mode applications at 780 nm.

Contribution

It introduces a method to monitor and control fiber transmittance during tapering, improving mode management in tapered optical fibers.

Findings

Transmittance evolution reflects mode coupling and cutoff.

Controlled tapering achieves desired mode properties.

Evanescent wave mapping confirms mode behavior.

Abstract

We have produced high transmission sub-wavelength tapered optical fibers for the purpose of whispering gallery mode coupling in fused silica microcavities at 780 nm. A detailed analysis of the fiber transmittance evolution during tapering is demonstrated to reflect precisely the mode coupling and cutoff in the fiber. This allows to control the final size, the number of guided modes and their effective index. These results are checked by evanescent wave mapping measurements on the resulting taper.