Fibre coupled dual-mode waveguide interferometer with $\lambda $/130 fringe spacing

TL;DR

This paper reports on a fibre-coupled dual-mode waveguide interferometer achieving a fringe spacing of approximately λ/130, significantly smaller than previous results, through predictions and measurements of its operation.

Contribution

It introduces a novel dual-mode waveguide interferometer with an unprecedentedly small fringe spacing of about λ/130, advancing the precision of fiber-optic interferometric sensors.

Findings

Complete switching cycle achieved with a 10 nm change in waveguide width

Fringe spacing of approximately λ/130, an order of magnitude smaller than prior reports

Experimental results match theoretical predictions

Abstract

Predictions and measurements of a multimode waveguide interferometer operating in a fibre coupled, ``dual-mode'' regime are reported. With a 1.32 micrometer source, a complete switching cycle of the output beam is produced by a 10.0 nanometer incremental change in the 8.0 micrometer width of the hollow planar mirror waveguide. This equates to a fringe spacing of $\sim\lambda /130$. This is an order of magnitude smaller than previously reported results for this form of interferometer.