High-Performance Tunable Multichannel Absorbers Coupled with Graphene-Based Grating and Dual-Tamm Plasmonic Structures

Plasmonics - We present a hybrid Tamm system targeting the tunable multichannel absorber. The proposed optical absorber is analyzed and investigated by using the transfer matrix method (TMM). The...     

Tunable Terahertz Plasmonic Perfect Absorber Based on T-Shaped InSb Array

High absorption efficiency is particularly desirable for various microtechnological applications. In this paper, a nearly perfect terahertz absorber for transverse magnetic (TM) polarization based on T-shaped InSb array is proposed and numerically investigated. Incident wave at the Fabry-Perot resonant frequency can be totally absorbed into the narrow grooves between the two adjacent T-shaped InSb arms. The absorption mechanism is theoretically and numerically studied by using the Fabry-Perot model and the finite element method (FEM), respectively. It is found that the proposed absorber has large angle tolerance. Moreover, the absorption peak can be controlled by varying the temperature. Furthermore, a new absorption peak will emerge while breaking the symmetry of the T-shaped InSb array. This tunable and angle-independent THz perfect absorber may find important applications in THz devices such as microbolometers, coherent thermal emitters, solar cells, photo detectors, and sensors.     

Tunable Multiple Fano Resonances and Stable Plasmonic Band-Stop Filter Based on a Metal-Insulator-Metal Waveguide

Plasmonics - A metal-insulator-metal (MIM) waveguide consisting of two stub resonators and a ring resonator is proposed, which can be used as refractive index sensor and stop-band filter at the...     

Tunable Plasmonic Absorber Based on Propagating and Localized Surface Plasmons Using Metal-Dielectric-Metal Structure

We propose a metal-dielectric-metal super absorber based on propagating and localized surface plasmons which exhibits a near perfect absorption in the visible and near-infrared spectrum. The absorber consists of Ag/Al₂O₃/Al triple layers in which the top Al layer is a periodic nano disk array. The absorption spectrum can be easily controlled by adjusting the structure parameters including the period and radius of the nano disk and the maximal absorption can reach 99.62 %. We completely analyze the PSPs and LSPs modes supported by the MDM structure and their relationship with the ultrahigh absorption. Moreover, we propose a novel idea to further enhance the absorption by exciting the PSPs and high-order LSPs modes simultaneously, which is different from the previous works. This kind of absorber using stable inexpensive Al instead of noble metal Au or Ag is an appropriate candidate for photovoltaics, spectroscopy, photodetectors, sensing, and surface-enhanced Raman spectroscopy (SERS).     

Tunable Plasmonic Absorber Based on TiN-Nanosphere Liquid Crystal Hybrid in Visible and Near-Infrared Regions

In this paper, a tunable plasmonic absorber based on TiN-nanosphere/liquid crystal (LC) nanocomposite in visible and near-infrared regions is proposed. TiN-nanosphere/LC nanocomposite is a combination of titanium nitride (TiN) nanospheres dispersed in a host of LC and plays the main role in post fabrication tunability. The proposed absorber has three more than 90% absorption peaks and the absorption tunability of about 76 nm. It is shown that TiN-nanospheres are able to support localized surface plasmon resonance (LSPR). The Maxwell-Garnett theory is utilized to approximate the permittivity of the composite structure. Also, the effect of geometric parameters on the absorption is studied. Moreover, a single sheet of graphene is utilized to compensate the decrement of the absorption caused by the geometric parameters.     

Multiple-Channel Plasmonic Filter Based on Metal-Insulator-Metal Waveguide and Fractal Theory

Plasmonics - A multiple-channel plasmonic filter based on metal-insulator-metal waveguide and fractal theory is proposed. The sandwiched insulator layer is constructed by a series of dielectrics...     

Tunable Salisbury Screen Absorber Using Square Lattice of Plasmonic Nanodisk

We propose a novel polarization independent Salisbury screen absorber to provide tunable resonant absorption at terahertz (THz) frequencies. The Salisbury screen absorber is designed by using a planar array of thin gold nanodisks arranged in a square lattice. Certain configurations of Salisbury screen have multiple distinctive absorption bands that support near-unity/FWHM absorption bandwidth reaching 36 THz/169 THz, respectively. Moreover, the absorption bandwidth depends upon the optical thickness of the dielectric spacer between the metasurface and the metallic ground plane. The proposed tunable Salisbury screen absorber can find practical applications in photonic detection, imaging, sensing, and solar cells at optical frequencies.     

High-Performance Enhancement of a GaAs Photodetector Using a Plasmonic Grating

Plasmonics - In this study, we present and establish a gold surface plasmon polariton (SPP) GaAs photodetector that achieves high internal quantum efficiency (IQE). At a wavelength of...     

Design and Analysis of Infrared Tunable All-Optical Filters Based on Plasmonic Hybrid Nanostructure Using Periodic Nanohole Arrays

A tunable high transmission optical bandpass filter based on a plasmonic hybrid nanostructure, composed of a periodic array of nanocircles and nanoholes combining two isolated waveguides is introduced in this paper. The presented design improves the coupling, which results in a higher transmission peak. To study the filtering operation, different topologies are investigated. The transmission properties and the resonance wavelengths are adjusted by sweeping various geometrical parameters. A multimode spectrum for each of the topologies is obtained. A tunable bandgap and bandwidth can be obtained by adjusting the refractive index of the periodic nanostructure. We have reached a maximum quality factor and a small full width at half-maximum bandwidth with the maximum transmission values greater than 80%. The advantages of the presented structures which include the benefits of both plasmonic and periodic nanostructures are tunability, high detection resolution, and integrability at the nanoscale for optical applications.

     

High-quality Temperature Sensor Based on the Plasmonic Resonant Absorber

Plasmonics - Aiming at the achievement of temperature measurement with high sensitivity in the sub-wavelength scale, an all-metal meta-surface (AMMS)-based sensor is numerically demonstrated. Based...     

Polarization Filtering and Phase Controlling Metasurfaces Based on a Metal-Insulator-Metal Grating

Metasurfaces used in the manipulation of light beams have attracted growing interests owing to their unique electromagnetic properties in the subwavelength regime. However, most previously demonstrated single-layer metasurfaces are normally designed to realize one-fold function of either polarization or phase manipulation and suffer from low cross-polarization conversion efficiency and high-background, especially for transmissive metasurfaces. Here, a metasurface based on metal-insulator-metal (MIM) subwavelength grating is proposed to simultaneously achieve polarization filtering and phase controlling. The transmission coefficient reaches up to 78.9% and the polarization extinction ratio (ER = 20*log(T _TM /T _TE) is larger than 16.1 dB. A local abrupt phase difference covering 0–2π is introduced into transmitted light with the polarization direction vertical to the grating by artificially tailoring the geometrical parameters of MIM grating. Furthermore, background-free wavefront control and high-purity radial/azimuthal polarization are realized by the metasurfaces based on the MIM grating. This flexible and high-efficient scheme of full control wavefront and polarization promises an unprecedented progress of spatial vectorial beams modulation and enable the realization of novel optical components.     

Tunable Plasmonic Resonances in Hexagonally Ordered Gold Nanostructure Arrays with Increasing Interstice Size

Plasmonics - Gold nanostructure arrays were fabricated by combining colloidal lithography with inclined reactive ion etching and inclinded sputtering. Field emission scanning electron microscopy...     

Multiband Terahertz Metamaterial Absorber Based on Multipolar Plasmonic Resonances

Terahertz metamaterial absorbers (MMA) have found wide scope of research prospective, remarkably in the development of multiband absorbers. Considerable applications are established using these multiband absorbers in THz imaging, wireless communication and bolometric detectors. The MMA was built on a GaAs substrate of 30 µm thickness and the hexagonal metallic pattern was etched out on a gold layer of 0.4 µm thickness on the top surface. The underlying ground layer is metallic backed. This design realizes the multiband (9-bands) of absorption in the spectral region from 0.56 to 0.92 THz. The multiband absorption mechanism of the absorber was examined by electric field dispersion analysis and impedance matching concept. From the established results, the absorber exhibits nine bands within a narrow frequency range and secures promising applications in hyperspectral imaging, clinical sensing and detection.

     

Tunable Terahertz Filters Based on Graphene Plasmonic All-Dielectric Metasurfaces

A tunable terahertz filter based on graphene plasmonic all-dielectric metasurfaces is proposed and investigated numerically by using the finite-difference time-domain (FDTD) method. Especially, hybrid all-dielectric metasurfaces are used to make a whole single-sheet graphene forms two different conductivity patterns with the same gate voltage. The simulated results show that resonance wavelength is shifted significantly with the change of gate voltage. Besides, the transmittance spectra are also shifted with the change of the width of SiC, and the filter shows a polarization-dependent modulation property for the length and the width of SiC being 480 and 320 nm, respectively. In addition, the filter can be applied for refractive sensing because the transmittance spectra are shifted with the change of the background refractive index. The study could provide availability for versatile tunable terahertz graphene plasmonic metasurfaces.     

A High Performance Plasmonic Sensor Based on Metal-Insulator-Metal Waveguide Coupled with a Double-Cavity Structure

A high performance plasmonic sensor based on a metal-insulator-metal (MIM) waveguide coupled with a double-cavity structure consisting of a side-coupled rectangular cavity and a disk cavity is proposed. The transmission characteristics of the rectangular cavity and disk cavity are analyzed theoretically and the improvements of performance for the double-cavity structure compared with a single cavity are studied. The influence of structural parameters on the transmission spectra and sensing performance are investigated in detail. A sensitivity of 1136 nm/RIU with a high figure of merit of 51,275 can be achieved at the resonant wavelength of 1148.5 nm. Due to the high performance and easy fabrication, the proposed structure may be applied in integrated optical circuits and on-chip nanosensors.     

Plasmonic Variable Optical Attenuator Based on Liquid-Crystal Tunable Stripe Waveguides

A long-range surface plasmon polariton variable optical attenuator based on available nematic liquid crystals and polymers is proposed and theoretically investigated. It is demonstrated that the electro-optic control of the nematic molecular orientation is capable of tuning the level of index asymmetry of an Au stripe waveguide and the key properties of the fundamental long-range plasmonic mode, such as modal profile and propagation losses. By proper structural design and material selection, plasmonic in-line intensity modulators are designed, which exhibit very low power consumption, extinction ratios in excess of 30 dB, and insertion losses as low as 1 dB for a device length in the millimeter range. Such active plasmonic elements are envisaged to be used in interchip photonics bus interconnects.     

Tunable Multimode Plasmonic Filter Based on Side-Coupled Ring-Groove Joint Resonator

Plasmonics - A tunable multimode plasmonic filter is proposed by using a side-coupled ring-groove joint resonator. In addition to the integer resonance modes of the perfect ring resonator (RR),...     

Novel Multi-Broadband Plasmonic Absorber Based on a Metal-Dielectric-Metal Square Ring Array

Plasmonics - We numerically analyzed a simple and novel design of multi-broadband plasmonic absorber which consists of a planar array of thin gold square ring structures on dielectric/metal...     

Tunable Nearly Perfect Absorber Based on Graphene Metamaterials at the Mid-Infrared Region

Plasmonics - We propose the idea of a tunable nearly perfect absorber based on graphene metamaterial consisting of a periodically arranged graphene ribbons (bright mode) and the inverse slots in...