Coherent-perfect-absorber and laser for bound states in a continuum

TL;DR

This paper demonstrates that bound states in continuum and spectral singularities can coexist in a waveguide system, enabling new laser and absorber functionalities for photonic bound states within a continuous spectrum.

Contribution

It introduces a system where bound states in continuum and spectral singularities occur simultaneously, enabling novel laser and coherent-perfect-absorber applications.

Findings

Coexistence of bound states in continuum and spectral singularities in a waveguide.

Potential for experimental realization of lasers and perfect absorbers for photonic bound states.

System design allows control over emission and absorption along the waveguide.

Abstract

It is shown that two fundamentally different phenomena, the bound states in continuum and the spectral singularity (or time-reversed spectral singularity), can occur simultaneously. This can be achieved, in particular, in a rectangular core dielectric waveguide with embedded active (or absorbing) layer. In such a system a two-dimensional bound state in a continuum is created in the plane of a waveguide cross section and it is emitted or absorbed along the waveguide core. The idea can be used for experimental implementation of a laser or a coherent-perfect-absorber for photonic bound state that resides in a continuous spectrum.