Modal approach for tailoring the absorption in a photonic crystal membrane

TL;DR

This paper introduces a novel method using Time Domain Coupled Mode Theory and FDTD simulations to enhance and tailor resonant absorption in photonic crystal membranes, achieving up to 85% absorption.

Contribution

The paper presents a new approach combining theoretical modeling and simulations to significantly improve absorption in photonic crystal membranes, surpassing previous limits.

Findings

Achieved 85% resonant absorption in simulations.

Demonstrated 100% absorption potential with degenerate modes.

Provided design rules for tailoring absorption in photonic structures.

Abstract

In this paper, we propose a method for tailoring the absorption in a photonic crystal membrane. For that purpose, we first applied Time Domain Coupled Mode Theory to such a subwavelength membrane and demonstrated that 100% resonant absorption can be reached even for a symmetric membrane, if degenerate modes are involved. Design rules were then derived from this model in order to tune the absorption. Subsequently, Finite Difference Time Domain simulations were used as a proof of concept and carried out on a low absorbing material (extinction coefficient=10-2) with a high refractive index corresponding to the optical indices of amorphous silicon at around 720 nm. In doing so, 85% resonant absorption was obtained, which is significantly higher than the commonly reported 50% maximum value. Those results were finally analyzed and confronted to theory so as to extend our method to other materials, configurations and applications.