Ultrabroadband Absorption Enhancement via Hybridization of Localized and Propagating Surface Plasmons.

Tian Sang,Xun Wang,Xinshang Niu,Hongfei Jiao,Bin Ma,Guoqing Li,Xin Yin,Honglong Qi

doi:10.3390/nano10091625

Abstract

Broadband metamaterial absorbers (MAs) are critical for applications of photonic and optoelectronic devices. Despite long-standing efforts on broadband MAs, it has been challenging to achieve ultrabroadband absorption with high absorptivity and omnidirectional characteristics within a comparatively simple and low-cost architecture. Here we design, fabricate, and characterize a novel compact Cr-based MA to achieve ultrabroadband absorption in the visible to near-infrared wavelength region. The Cr-based MA consists of Cr nanorods and Cr substrate sandwiched by three pairs of SiO2/Cr stacks. Both simulated and experimental results show that an average absorption over 93.7% can be achieved in the range of 400–1000 nm. Specifically, the ultrabroadband features result from the co-excitations of localized surface plasmon (LSP) and propagating surface plasmon (PSP) and their synergistic absorption effects, where absorption in the shorter and longer wavelengths are mainly contributed bythe LSP and PSP modes, respectively. The Cr-based MA is very robust to variations of the geometrical parameters, and angle-and polarization-insensitive absorption can be operated well over a large range of anglesunder both transverse magnetic(TM)- and transverse electric (TE)-polarized light illumination.

Highlights

Light absorption enhancements in metamaterials have received intensive attention due to their diverse performances in a series of applications such as thermal emitters [1,2], sensors [3,4,5], photodetectors [6,7], photovoltaics [8,9], and optical imaging devices [10,11,12]
The electric dipole resonance can be induced by the metallic patterns and the magnetic dipole resonance can be excited by the anti-parallel currents between the interfaces of the metal and insulator layers
The Cr-based metamaterial absorbers (MAs) consists of Cr nanorods and Cr substrate sandwiched by three pairs of SiO2/Cr stacks

Summary

Introduction

Light absorption enhancements in metamaterials have received intensive attention due to their diverse performances in a series of applications such as thermal emitters [1,2], sensors [3,4,5], photodetectors [6,7], photovoltaics [8,9], and optical imaging devices [10,11,12]. The absorption performances of the Cr-based MA are insensitive to variations of the structural parameters, and the broadband features can be maintained even at the incident angle of 60◦ for bothtransverse magnetic(TM) and transverse electric (TE) polarizations. All these advantageous optical properties make our proposed structure a good candidate to improve various important applications such as photovoltaic devices, remote sensing and photodetectors

Design and Characterization of the Proposed MA

Physical Basis for Ultrabroadband Absorption Enhancement

Findings

Evaluation of Absorption Performances of the Proposed MA