Coexistence of Surface Lattice Resonances and Bound states In the Continuum in a Plasmonic Lattice

TL;DR

This study numerically investigates how surface lattice resonances and bound states in the continuum can coexist in a plasmonic lattice, controlled by the optical environment, with implications for biosensing and optoelectronics.

Contribution

It demonstrates the control of SLRs and BICs in plasmonic lattices through refractive index contrast, providing insights for designing advanced light-matter interaction devices.

Findings

SLRs cannot be excited with small refractive index contrast

Significant contrast enables both SLRs and BICs formation

Presence of symmetry-protected and accidental BICs in high contrast regimes

Abstract

We present a numerical study on a 2D array of plasmonic structures covered by a subwavelength film. We explain the origin of surface lattice resonances (SLRs) using coupled dipole approximation and show that the diffraction-assisted plasmonic resonances and formation of bound states in the continuum (BICs) can be controlled by altering the optical environment. Our study shows that when the refractive index contrast is small ( $\Delta$n < -0.1), the SLR cannot be excited, while a significant contrast ($\Delta$n > 0.3) not only sustains plasmonic-induced resonances but also forms both symmetry-protected and accidental BICs. The results can aid the streamlined design of plasmonic lattices in studies on light-matter interaction and applications in biosensors and optoelectronic devices.