Fano feature induced by a bound state in the continuum via resonant state expansion

Pavel S Pankin,Dmitrii N Maksimov,Ivan V Timofeev,Kuo-Ping Chen

doi:10.1038/s41598-020-70654-2

Abstract

We consider light scattering by an anisotropic defect layer embedded into anisotropic photonic crystal in the spectral vicinity of an optical bound state in the continuum (BIC). Using a resonant state expansion method we derive an analytic solution for reflection and transmission amplitudes. The analytic solution is constructed via a perturbative approach with the BIC as the zeroth order approximation. The solution is found to describe the collapsing Fano feature in the spectral vicinity of the BIC. The findings are confirmed via comparison against direct numerical simulations with the Berreman transfer matrix method.

Highlights

In this paper we considered light scattering by an anisotropic defect layer embedded into anisotropic photonic crystal in the spectral vicinity of an optical BIC
Using a resonant state expansion method we derived an analytic solution for reflection and transmission amplitudes
To the best of our knowledge this is the first full-wave analytic solution involving an optical BIC reported in the literature

Summary

Introduction

In this paper we propose a RSE approach to the problem of light scattering by an anisotropic defect layer (ADL) embedded into anisotropic photonic crystal (PhC) in the spectral vicinity of an optical bound state in the continuum (BICs). The resonant states are the eigenmodes of Maxwell’s equations [1] with reflectionless boundary conditions in the PhC arms. The equation for resonant eigenfrequencies can be obtained by matching the general solution in the ADL to the outgoing, both propagating and evanescent, waves in the PhC arms.

Results

Conclusion