Compact photonic-crystal superabsorbers from strongly absorbing media

TL;DR

This paper introduces a method to achieve near-perfect absorption in compact photonic-crystal structures made from strongly absorbing media by tuning structural parameters to meet a reflectionless condition, demonstrated with a SiC-based prototype.

Contribution

It provides a clear recipe for achieving reflectionless conditions in lossy photonic crystals, enabling near-perfect absorption in ultra-thin structures, which is a novel approach in the field.

Findings

Achieved over 90% absorption in a subwavelength layer

Designed a three-layer SiC-BaF2-SiC photonic crystal

Demonstrated near-perfect absorption with total thickness less than λ/3

Abstract

We present a route to near-perfect absorption in compact photonic-crystal (PC) structures constructed from strongly absorbing media that are typically highly reflective in bulk form. Our analysis suggests that the key underlying mechanism in such PC superabsorbers is the existence of a PC-band-edge reflectionless condition. Although the latter is by default uncharacteristic in photonic crystals, we propose here a clear recipe on how such condition can be met by tuning the structural characteristics of one-dimensional lossy PC structures. Based on this recipe we constructed a realizable three-layer SiC-BaF2-SiC PC operating within the Reststrahlen band of SiC. We demonstrate near-perfect absorption in this prototype of total thickness smaller than lamda/3, where more than 90% of the impinging light is absorbed by the top deep-subwavelength layer of thickness ~lamda/1100. We believe our study will inspire new photonic-crystal-based designs for extreme absorption harnessing across the electromagnetic spectrum.