Abstract
An ultrabroadband, omnidirectional, and polarization-insensitive absorber based on cascaded nanorod arrays (CNAs) is numerically demonstrated, and an average absorptivity of 98.2% with a relative absorption bandwidth (RAB) of 149.8% can be achieved in the 0.38–2.65 μm wavelength range. The proposed CNA-based absorber requires only several pairs of multilayers to achieve excellent absorption performance. More significantly, the physical mechanism for this intriguing ultrabroadband absorption results from the synergistic effect of localized surface plasmon (LSP) and plasmonic resonant cavity (PRC) modes, which is fundamentally different from the tapered metal/dielectric multilayer-based absorbers associated with the slow-light mode. We investigated the absorption properties of the CNA-based metasurface by using the impedance theory, which indicates that the impedance of the structure matches well with the impedance of the free space from the visible to near-infrared wavelength range. In addition, the absorption properties of the CNA-based metasurface are robust to the variation of the structural parameters and the metal/dielectric materials, and ultrabroadband absorption performance can be maintained within 0–60° for both TM and TE modes.
Highlights
Plasmonic absorbers can function as crucial components for various applications such as sensing [1,2], photodectors [3], thermal emitters [4,5], photovoltaics [6,7], etc
Inspired by these earlier works, here we demonstrate a novel ultrabroadband, omnidirectional, and polarization-insensitive absorber based on cascaded nanorod arrays (CNAs)
The physical mechanism for ultrabroadband light absorption of the CNA-based absorber results from localized surface plasmon (LSP) mode, plasmonic resonant cavity (PRC) mode, and their hybrid modes, which is fundamentally different from the tapered metal/dielectric multilayer-based absorbers associated with the slow-light mode
Summary
Plasmonic absorbers can function as crucial components for various applications such as sensing [1,2], photodectors [3], thermal emitters [4,5], photovoltaics [6,7], etc. The metal-insulator-metal (MIM) nanopatterned structures are the main schemes to achieve perfect light absorption enhancement [8] In this configuration, strong electromagnetic coupling could be excited between the metallic pattern and the metallic substrate in a small wavelength range due to magnetic or electric resonance. Despite the elaborate study of nanostructured plasmonic absorbers, absorption performance that combines the advantages of high absorption efficiency, ultrabroad bandwidth, and omnidirectional characteristics is still highly desired. Inspired by these earlier works, here we demonstrate a novel ultrabroadband, omnidirectional, and polarization-insensitive absorber based on cascaded nanorod arrays (CNAs). TM and TE polarizations in the range of 0–60◦
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