Topology optimization of a superabsorbing thin-film semiconductor metasurface

TL;DR

This paper introduces a computational inverse design approach for creating broadband-absorbing metasurfaces using a time-domain adjoint method, enabling the design of complex structures with unprecedented absorption performance.

Contribution

The authors develop a novel topology optimization framework utilizing a time-domain adjoint method for broadband metasurface design with arbitrary dispersive media.

Findings

Designed Silicon-on-insulator metasurfaces with enhanced broadband absorption.

The method captures dispersive media response over wide spectral ranges.

Applicable to various linear materials, including dielectric and plasmonic.

Abstract

We demonstrate a computational inverse design method for optimizing broadband-absorbing metasurfaces made of arbitrary dispersive media. Our figure of merit is the time-averaged instantaneous power dissipation in a single unit cell within a periodic array. Its time-domain formulation allows capturing the response of arbitrary dispersive media over any desired spectral range. Employing the time-domain adjoint method within a topology optimization framework enables the design of complex metasurface structures exhibiting unprecedented broadband absorption. We applied the method to a thin-film Silicon-on-insulator configuration and explored the impact of structural and (time-domain inherent) excitation parameters on performance over the visible-ultraviolet. Since our incorporated material model can represent any linear material, the method can also be applied to other all-dielectric, plasmonic, or hybrid configurations.