A Broadband Superabsorber at Optical Frequencies: Design and Demonstration

TL;DR

This paper introduces a novel analytical framework for designing broadband super absorbers at optical frequencies, achieving near-unity absorption over a broad spectrum with polarization insensitivity and simplified design process.

Contribution

The authors develop an analytical method for designing broadband super absorbers, significantly reducing design time compared to full wave simulations, and demonstrate high-performance experimental results.

Findings

Average absorption of ~97% from 450 to 950 nm

Near unity absorption (99.36%) in 500-850 nm range

Experimental absorption over 98% across 450-950 nm at 20° incident angle

Abstract

Metasurface based super absorbers exhibit near unity absorbance. While the absorption peak can be tuned by the geometry/size of the sub-wavelength resonator, broadband absorption can be obtained by placing multiple resonators of various size or shapes in a unit cell. Metal dispersion hinders high performance broadband absorption at optical frequencies and careful designing is essential to achieve good structures. We propose a novel analytical framework for designing a broadband super absorber which is much faster than the time consuming full wave simulations that are employed so far. Analytical expressions are derived for the wavelength dependency of the design parameters, which are then used in the optimization of broadband absorption. Numerical simulations report an average polarization-independent absorption of ~97 in the 450 to 950 nm spectral region with a near unity absorption (99.36) in the 500 to 850 nm region. Experimentally, we demonstrate an average absorption over 98 in the 450 to 950 nm spectral region at 20 degree incident angle The designed super absorber is polarization insensitive and has a weak launch angle dependency. The proposed framework simplifies the design process and provides a quicker optimal solution for high performance broadband super absorbers.