Ultraviolet broadband plasmonic absorber with dual visible and near-infrared narrow bands

Broadband light absorption by a hemispherical concentric nanoshell array

Achieving highly efficient broadband absorption is an important research area in nanophotonics. In this paper, a novel method is proposed to design broadband near-perfect absorbers, consisting of a four-layer hemispherical concentric nanoshell array. The proposed nanostructure supports absorptivity exceeding 95% in the entire visible region, and the absorption bandwidth is determined by the interaction or 'hybridization' of the plasmons of the inner and outer metal-based nanoshells. Moreover, the designed absorber has wide-angle capability and is insensitive to polarization. The simple structure, as well as the stable absorption properties, suggests that such core-shell nanostructures can serve as a potential candidate for many applications such as solar energy harvesting, photo-detection, and emissivity control.

Visible-Range Multiple-Channel Metal-Shell Rod-Shaped Narrowband Plasmonic Metamaterial Absorber for Refractive Index and Temperature Sensing

Multiple resonance modes in an optical absorber are necessary for nanophotonic devices and encounter a challenge in the visible range. This article designs a multiple-channel plasmonic metamaterial absorber (PMA) that comprises a hexagonal arrangement of metal-shell nanorods in a unit cell over a continuous thin metal layer, operating in the visible range of the sensitive refractive index (RI) and temperature applications. Finite element method simulations are utilized to investigate the physical natures, such as the absorptance spectrum, magnetic flux and surface charge densities, electric field intensity, and electromagnetic power loss density. The advantage of the proposed PMA is that it can tune either three or five absorptance channels with a narrowband in the visible range. The recorded sensitivity and figure of merit (S, FOM) for modes 1-5 can be obtained (600.00 nm/RIU, 120.00), (600.00 nm/RIU, 120.00 RIU^-1), (600.00 nm/RIU, 120.00 RIU^-1), (400.00 nm/RIU, 50.00 RIU^-1), and (350.00 nm/RIU, 25.00 RIU^-1), respectively. Additionally, the temperature sensitivity can simultaneously reach 0.22 nm/°C for modes 1-3. The designed PMA can be suitable for RI and temperature sensing in the visible range.

Selective MOCVD synthesis of VO2 crystals on nanosharp Si structures

High-quality single VO₂ nanocrystals and ordered arrays of VO₂ nanorings were selectively synthesized by chemical vapor deposition (CVD) respectively on the tip apices and on the sidewall scallops.

Tunable phase change polaritonic perfect absorber in the mid-infrared region

Realizing tunable light-polaritons interaction, such as perfect absorption in a controllable and compact manner holds great promise in nanophotonic systems. In this work, we engineer the hyperbolic surface phonon polaritons and surface plasmons polaritons to dynamically tune the perfect absorption in mid-infrared by combing the two van der Waals materials: the natural hyperbolic material hBN and phase change material VO₂. Two spectrally separated and physically distinct perfect absorption peaks are alternatively observed and can be tuned through changing the temperature. The absorption in the resonant wavelengths can reach around 100%. We also demonstrate the flexibility of the absorber by investigating the absorption dependence on the polarization state and angle of incidence. The structural parameters sweep also confirms the robustness of our design. Our findings may open new possibilities to many versatile minimized applications such as optical modulators, optical switching, and temperature control system.

Ultra-broadband metamaterial absorber based on cross-shaped TiN resonators

In this paper, a novel broadband plasmonic absorber based on cross-shaped titanium nitride (TiN) resonators in the ultraviolet, visible, and near-infrared regions is presented. The proposed perfect solar absorber consists of periodic arrays of cross-shaped TiN resonators located on a stack of ${{\rm SiO}_2}/{\rm TiN}$SiO₂/TiN layers. By using the finite-difference time-domain method, the effects of variations of the thickness and radius of the elliptical metasurface resonators on the absorption are comprehensively investigated. The cross-shaped metamaterial absorber exhibits an averaged absorption of 90%, ranging from 200 to 3000 nm, and shows over 90% absorption from 200 to 2500 nm. Furthermore, the proposed absorber indicates absorption efficiency over 80% for an oblique incidence up to 50 deg for both TE- and TM-polarized light. These features make the proposed solar absorber usable in many solar-based applications, imaging, and thermal emitting.