Metal-free plasmonic refractory core-shell nanowires for tunable all-dielectric broadband perfect absorbers

Abstract

In this work, we numerically demonstrate a new facile strategy for all-dielectric broadband optical perfect absorbers. A monolayer refractory titanium oxide and nitride (TiN/TiO2) core-shell nanowires array is used to form the grating on the opaque TiN substrate. Multiple resonant absorption bands are observed in the adjacent wavelength range, which therefore leads to the formation of an ultra-broadband absorption window from the visible to the infrared regime. The maximal absorption reaches 95.6% and the average absorption efficiency in the whole range (0.5–1.8 µm) is up to 85.4%. Moreover, the absorption bandwidth can be feasibly adjusted while the absorption efficiency can be still maintained in a high level via tuning the polarization state. Furthermore, the absorption window is observed to be highly adjustable in the wavelength range, showing a nearly linear relationship to the shell's index. These features not only confirm the achievement of the broadband perfect absorption but also introduce feasible ways to artificially manipulate the absorption properties, which will hold wide applications in metal-free plasmonic optoelectronic devices such as the solar harvesting, photo-detection, and thermal generation and its related bio-medical techniques.

Dynamically tunable terahertz multi-band perfect absorber based on photosensitive silicon

“…However, these absorbers have the determination of fixed absorption frequency, and various tunable absorbers have been proposed in recent years, based on electrical tuning, phase change materials, pressure tuning, and optical tuning methods [32][33][34][35][36][37][38][39][40][41][42][43]. For example, a tunable reflective lens based on graphene hypersurface was proposed by Ding et al [32].…”

“…Ren et al proposed a vanadium dioxide (VO 2 )-gold structure enabling switching between dual-frequency asymmetric transmission and perfect absorption of circularly polarized light in the near-infrared region [33]. Zhang et al achieved broadband absorption by forming gratings consisting of arrays of core-shell nanowires on a substrate, and the absorption window could be adjusted by tuning the polarization state [34]. In the field of narrowband absorbers, Cheng et al designed a cross-shaped structure that can realize perfect terahertz wave absorber/reflector switching, based on the excitation of the pump beam on photoconductive silicon [35].…”

A tunable all dielectric perfect absorber based on hybrid graphene-dielectric metasurface in the mid-infrared regime

“…To overcome these di culties, an alternative approach using dielectric metasurface to form metal free absorber has recently been reported [9][10][11][12]. The metasurface can be regarded as a quasi twodimensional metamaterial with sub-wavelength thickness.…”

“…However, this kind of structure often requires a thicker highly doped silicon substrate, which is not conducive to the integration of the metal free absorber. In addition, some researchers [11][12] take advantage of refractory with good light absorption in the short wavelength, and using them as substrates can also greatly increase the absorption e ciency of the absorber. However, due to the characteristics of refractory, the working band of the refractory-based absorber can only be limited to the short wavelength.…”