Formation of Bound States in the Continuum in Hybrid Plasmonic-Photonic Systems

TL;DR

This paper demonstrates the realization of bound states in the continuum (BICs) within hybrid plasmonic-photonic systems, overcoming loss challenges and enabling high-Q localized states with potential for controlling light propagation.

Contribution

It introduces a hybrid plasmonic-photonic structure supporting both symmetry protected and Friedrich-Wintgen BICs, with strong coupling effects and band diagram modifications.

Findings

Support for symmetry protected and Friedrich-Wintgen BICs in hybrid systems

High Rabi splitting of 150 meV indicating strong coupling

Potential for supporting stopped light at off-{ extGamma} angles

Abstract

A bound state in the continuum (BIC) is a localized state of an open structure with access to radiation channels, yet it remains highly confined with, in theory, infinite lifetime and quality factor. There have been many realizations of such exceptional states in dielectric systems without loss. However, realizing BICs in systems with losses such as plasmonics remains a challenge. In this Letter, we explore the possibility of realizing BICs in a hybrid plasmonic-photonic structure consisting of a plasmonic grating coupled to a dielectric optical waveguide. The plasmonic-photonic system supports two distinct groups of BICs: symmetry protected BICs at the {\Gamma}-point and off-{\Gamma} Friedrich-Wintgen BICs. The photonic waveguide modes are strongly coupled to the gap plasmons in the grating leading to an avoided crossing behavior with a high value of Rabi splitting of 150 meV. Moreover, we show that the strong coupling significantly alters the band diagram of the hybrid system revealing opportunities for supporting stopped light at an off-{\Gamma} wide angular span.