Dispersion Engineered Metastructures Enabling Broadband Angular Selectivity

TL;DR

This paper presents a dispersion engineering and topology optimization approach to design 2D metastructures with broadband, isotropic angular selectivity, demonstrated through experimental metastructures with complementary angular responses.

Contribution

The work introduces a novel dispersion engineering method combined with topology optimization to achieve broadband angular selectivity in optically thin metastructures.

Findings

Achieved isotropic angular selectivity over ~20% bandwidth.

Demonstrated metastructures with complementary angular responses.

Operation bandwidth exceeds GMR linewidths due to tailored interactions.

Abstract

Angle-selective optical devices are of importance to several applications such as photovoltaics, high-sensitivity photodetectors and displays. There are several approaches to realizing angular selectivity, but it remains challenging to obtain isotropic responses over large spectral bandwidths in optically thin structures. We introduce a dispersion engineering approach coupled with topology optimization to design 2D metastructures, leveraging guided-mode resonances (GMRs), that exhibit isotropic angular selectivity over relative bandwidths of approximately 20%. We experimentally demonstrate metastructures with complementary angular selectivities, either scattering light strongly near normal incidence and transmitting efficiently at higher incident angles, or vice versa. A key finding is that these designs enable operation over spectral bandwidths greater than the GMR linewidths would suggest, a result of carefully tailored interactions between the Fabry-Perot background and resonantly scattered light. This work marks a significant step forward for the realization of broadband, angle-selective scattering in readily fabricated structures of subwavelength thickness, and enables new possibilities in sensing, analog information processing, high-efficiency photovoltaics, and displays.