Point-Defect-Localized Bound States in the Continuum in Photonic Crystals and Structured Fibers

TL;DR

This paper demonstrates that point defects in 2D photonic crystals can support bound states in the continuum through symmetry mismatch, enabling light confinement without bandgaps and potential applications in structured fibers with slow light.

Contribution

It introduces a novel mechanism for BICs in photonic crystals based on symmetry mismatch, applicable in fiber geometries for slow light and enhanced nonlinear interactions.

Findings

Point defects support BICs via symmetry mismatch.

BICs occur without bandgaps, offering alternative confinement.

BICs can propagate in fibers with arbitrarily small group velocity.

Abstract

We show that point defects in two-dimensional photonic crystals can support bound states in the continuum (BICs). The mechanism of confinement is a symmetry mismatch between the defect mode and the Bloch modes of the photonic crystal. These BICs occur in the absence of bandgaps and therefore provide an alternative mechanism to confine light. Furthermore, we show that such BICs can propagate in a fiber geometry and exhibit arbitrarily small group velocity which could serve as a platform for enhancing non-linear effects and light-matter interactions in structured fibers.