Rectified phase-matching equation for fiber mode converter gratings using two-mode interference

TL;DR

This paper introduces a new mathematical method to accurately predict the resonance wavelength of fiber mode converter gratings, enabling precise design and characterization using a single experimental measurement.

Contribution

A novel rectified phase-matching equation linking two-mode interference with mode conversion, allowing accurate resonance wavelength prediction from minimal experimental data.

Findings

Predicted resonance wavelengths within 0.004 relative error

Validated method across various fiber and grating conditions

Enhanced precision in fiber grating design

Abstract

The resonance wavelength, where a fiber mode converter grating written using periodic external perturbations achieves phase matching, is both a critical design parameter and a device parameter. However, a method to precisely predict the resonance wavelength for any new fiber and grating writing apparatus has been missing so far. The missing link was the lack of direct experimental methods to estimate the modified intermodal phase after writing with external perturbations. The presented method can make this estimation from a single experiment, over a broad wavelength range, based on a novel mathematical connection between two-mode interference and mode conversion. Using the novel methods, experimentally measured resonance wavelengths for different pitch and irradiation conditions have been predicted within relative errors of 0.004.