Optical super-resonance in a customized PT-symmetric system of hybrid interaction

We investigate the optical resonances in coupled meta-atoms with hybrid interaction pathways. One interaction pathway is the directly near-field coupling between the two meta-atoms. The other interaction pathway is via the continuum in a waveguide functioned as a common bus connecting them. We show that by properly introducing gain or loss into the meta-atoms, the hybrid optical system becomes parity-time (PT) symmetric, in which the effective coupling rate can be customized by manipulating the length of the waveguide. At the exact phase of the customized PT symmetry, the coupled meta-atoms support discrete super-resonant modes that can be observed from the transmission spectra as extremely sharp peaks. At an exception point where the eigenmodes coalesce, albeit the transmission curve is flat, a high-Q factor of the localized field in the meta-atoms can be obtained. Similarities of the super-resonance with the bound states in the continuum (BICs) are discussed. This investigation promotes our understanding about the ways in realizing high-Q optical resonance especially by manipulating the distributions of loss and gain via the concepts of PT and BICs. Many attractive applications are expected. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Automated summary

The study explores optical resonances in coupled meta-atoms with hybrid interaction pathways, making the hybrid optical system PT symmetric by introducing gain or loss. This allows for customization of the effective coupling rate and supports discrete super-resonant modes. At specific phases, extremely sharp peaks in transmission spectra are observed, and at exceptional points, a high-Q factor of the localized field can be obtained.