Talbot interference of whispering gallery modes

TL;DR

This paper explores the Talbot interference effect in whispering gallery modes within multimode fibers, demonstrating fractional Talbot effects for optical beam splitting and multiplexing using accessible components.

Contribution

It introduces the use of whispering gallery modes in step-index multimode fibers to realize high-order fractional Talbot effects for optical beam splitting and multiplexing.

Findings

Demonstrated 9- and 30-port beamsplitters using fractional Talbot effect

Achieved efficient interfacing with single-mode fibers for signal multiplexing

Extended Talbot effect applications to widely available multimode fibers

Abstract

The Talbot self-imaging phenomenon is a fundamental interference effect that is natural to all waves with a periodic structure. We theoretically and experimentally study the Talbot effect for optical waves in the transverse angular domain using whispering-gallery modes of step-index multimode fibers, which carry a high orbital angular momentum and fulfill the required quadratic dispersion relation. By using the complex interference along the core-cladding interface of these fibers, we experimentally demonstrate that the high-order fractional Talbot effect can be used to implement 9- and 30-port beamsplitters using only off-the-shelf components in a compact arrangement. In addition, we show that the beamsplitters can be efficiently interfaced with single-mode fibers, such that our work not only extends the recent developments on the angular Talbot effect to widely available step-index multimode fibers, but also demonstrates a powerful application as a signal multiplexer, which becomes more compact as the number of channels is increased.