Embedded Scattering Eigenstates Using Resonant Metasurfaces

TL;DR

This paper proposes a novel method to realize optical embedded eigenstates in nanostructures using ultrathin metasurfaces of nanoparticles, overcoming material loss issues with gain media, enabling advanced nanophotonic applications.

Contribution

It introduces a new approach to achieve embedded eigenstates in nanostructures using metasurfaces and gain media to compensate losses, which was previously challenging.

Findings

Arrays of lossless nanoparticles can realize embedded eigenstates.

Gain-coated nanoparticles can compensate for material losses.

Potential applications include lasers, filters, and sensors.

Abstract

Optical embedded eigenstates are localized modes of an open structure that are compatible to radiation yet they have infinite lifetime and diverging quality factors. Their realization in nanostructures finite in all dimensions is inherently challenging, because they require materials with extreme electromagnetic properties. Here we develop a novel approach to realize these bound states in the continuum using ultrathin metasurfaces composed of arrays of nanoparticles. We first show that arrays of lossless nanoparticles can realize the condition for embedded eigenstates, and then explore the use of Ag nanoparticles coated with gain media shells to compensate material loss and revive the embedded eigenstate despite realistic loss in plasmonic materials. We discuss the possible experimental realization of the proposed structures and provide useful guidelines for practical implementation in nanophotonics systems with largely enhanced light-matter interactions. These metasurfaces may lead to highly efficient lasers, filters, frequency comb generation and sensors.