Flat-Top Reflection Characteristics in Metal-Dielectric-Metal Plasmonic Waveguide Structure Side Coupled with Cascaded Double Cavities

Based on a metal-dielectric-metal (MDM) plasmonic waveguide side coupled with a single cavity, we rebuild such resonator system by cascading double side-coupled cavities to obtain flat-top reflection response over a frequency bandwidth. The increased coherent scattering path provides an additional freedom to engineer the complex interference between the cavity modes and the waveguide mode. By decomposing the compound cavity modes into two decoupled resonances, we analyze the conditions to realize flat-top reflection response. The physics behind the flat-top reflection characteristics is found to be originated from the interference interaction between the two cavities through examining the cavity excitations and the reflected power response. Temporal coupled-mode theory and finite difference time domain method are utilized as theoretical and numerical tools which convince each other.     

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).     

Low Loss Plasmonic Bragg Gratings with a Trench Plasmonic Waveguide

Plasmonics - We designed plasmonic Bragg gratings based on a plasmonic trench waveguide and calculated the characteristics of the designed structure. Conventional plasmonic Bragg gratings are...     

A Wavelength Demultiplexing Structure Based on the Multi-Teeth-Shaped Plasmonic Waveguide Structure

In this paper, a wavelength demultiplexing structure based on multi-teeth-shaped metal-insulator-metal (MIM) plasmonic waveguide is designed and numerically studied using the finite-difference time-domain (FDTD) method. Investigating the characteristics of a multi-teeth-shaped plasmonic waveguide structure reveals that with the design of the structure, it was possible to create a mode inside the bandgap of the filter. Based on the created mode inside the bandgap of the filter, the demultiplexer structure has been proposed and investigated. By changing the geometric parameters of the structure, the transmission wavelength of the demultiplexer channel can be adjusted. The proposed demultiplexer can be used in integrated optical circuits.

     

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...     

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.     

Modulating Plasmonic Sensor with Graphene-Based Silicon Grating

We propose a modulating plasmonic structure device which is composed of a single layer graphene above the silicon Bragg grating with the silica spacer layer. This graphene-based plasmonic modulation provides a broad stop-band with high tunability in the mid-infrared region of the transmission spectra achieved by altering the geometrical parameters of the silicon grating and the gate voltage. By engineering, a phase discontinuity into the graphene-based Bragg grating, we can selectively open a transmission window in the previous stop-band spectra. These proposed graphene-based structures are easy to fabricate and operate, which have potential applications as ultra-compact high-sensitivity sensors.     

Tunable Surface-Enhanced Raman Spectroscopy via Plasmonic Coupling Between Nanodot-Arrayed Ag Film and Ag Nanocube

Herein, a flexible surface-enhanced Raman spectroscopy (SERS) substrate composed of nanodot-arrayed Ag film and Ag nanocubes was fabricated through a simple method. The large-area nanodot-arrayed Ag film was produced at low cost and high reproducibility. The experimental results show that the coupled structure produces a much stronger SERS signal than the Ag nanocube alone and the isolated nanodot-arrayed Ag film. Furthermore, the coupling effect is sensitive to geometrical parameter of the period of the dot-array. Numerical simulations are performed to verify the electric field enhancement of the composite SERS substrate and support the experimental results.     

A Hybrid Plasmonic Modulator Based on Graphene on Channel Plasmonic Polariton Waveguide

A hybrid plasmonic modulator based on graphene on channel plasmonic polariton waveguide was proposed to overcome the difficulty in achieving high-speed modulation on the nanometric plasmonic waveguide platform. The extinction ratio and the figure of merit of the proposed modulator were analyzed in detail, and a tradeoff between them was found due to the intrinsic loss of the channel plasmonic polariton waveguide. And an optimized hybrid plasmonic modulator with large modulation bandwidth of 0.662 THz, low power consumption of 118.7 fJ/bit, and short device length of 7.680 μm was obtained theoretically. In addition, the proposed hybrid plasmonic modulator based on graphene on channel plasmonic polariton waveguide is easy to fabricate and provides a potential solution for the high-speed plasmonic modulator.

     

Tunable Plasmonic Dispersion and Strong Coupling in Graphene Ribbon and Double Layer Sheets Structure

Based on the interplay between propagating surface plasmon polaritons (PSPs) in graphene ribbon and double layer sheets structure, we theoretically demonstrate a tunable strong coupling mechanism significantly different from reported conventional noble metal nanostructures. The strong electromagnetic coupling between the low order antisymmetric and high order symmetric PSPs modes occurs due to the intersections of dispersion curves, which leads to a modification of plasmonic dispersion and multiple significant anti-crossing regions. Of particular, this strong coupling is controllable through external gate voltage of graphene sheets or ribbon. The results offer an effective regime to dynamically tune the interaction of graphene PSPs, which may find applications in the field of nanophotonic devices in the mid-infrared range.     

Ultra-Subwavelength and Low Loss in V-Shaped Hybrid Plasmonic Waveguide

A new kind of hybrid plasmonic waveguide is proposed, and its propagation properties are investigated using the finite-element method. This waveguide consists of a V-shaped silver nanowire embedded in a low-index dielectric cladding above a semiconductor substrate, which can confine light in the subwavelength region with a long propagation length. The field distribution, the mode effective index, the propagation length, and the normalized mode area of the hybrid mode supported by the waveguide are investigated at the wavelength of 1550 nm, which are dependent on the geometric parameters.     

Plasmonic Filter Using Metal-Insulator-Metal Waveguide with Phase Shifts and its Transmission Characteristics

Plasmonics - A plasmonic filter based on metal-insulator-metal (MIM) waveguide with phase shifts is proposed, and the corresponding transmission characteristics are investigated. Since the...     

High-Quantum Efficiency of the Plasmonic Photodetectors-Based on Coupling Between Ag Nanoparticles and Ag Nanograting Electrodes

The plasmonic effects due to the coupling of silver spherical nanoparticles with silver nanograting electrodes on active medium of the photo detector are investigated. Calculations show that the coupling of nanoparticles and nanograting electrodes at the surface of active medium lead to reflection wave into the active medium, and electrodes can participate in the absorption and quantum efficiency. Calculations show that the addition of nanograting electrodes to the structure can lead to increase the absorption coefficient up to 120% respect to the plasmonic structure containing only nanoparticles and about 4.5 times that of conventional (metal-semiconductor -metal ) MSM photo detectors.

     

Plasmonic Waveguide Filters Based on Tunneling and Cavity Effects

This work presents a bandstop plasmonic filter that comprises a metal–insulator–metal (MIM) waveguide and a few pairs of strip cavities that are embedded in the metal. The strip cavity acts as both a near-field antenna and an MIM resonator. The central frequency and the bandwidth of the forbidden band are inversely related to the cavity length and the cavity-to-waveguide distance, respectively. These results correlate with the predictions of the ring resonator model but only under the resonant condition that double the effective length of cavity is an integer multiple of the guiding wavelength in the cavity.     

Tunable Electromagnetically Induced Transparency-Like in Plasmonic Stub Waveguide with Cross Resonator

Plasmonics - An analog of electromagnetically induced transparency (EIT) is investigated in a metal-insulator-metal (MIM) waveguide structure consisting of a stub waveguide and a side-coupled cross...     

Power Breakdown Threshold of a Plasmonic Waveguide Filter

The services provided by satellite communications are continuously increasing, and this demands a higher bandwidth and power consumption. The current devices involved with this problem are waveguides and filters. Recent research shows the technological limit of these macro-devices, so that it is necessary to work in new designs using higher frequency than microwaves, because the power consumption would be reduced and the data rate would increase from 195 Gbps to 5,600 Tbps. The use of optical communications in satellites would help to satisfy the demand of new services. In this article, the use of plasmonic waveguide filters is proposed to demultiplex signals in real time instead of the use of digital grating processors (DGP). These filters operate with surface plasmon polaritons in a metal-insulator-metal structure. Their power breakdown threshold is obtained and analyzed in a variable pressure range and operating at different wavelengths.     

Effective Coupling of Incident Light Through an Air Region into an S-Shape Plasmonic Ag Nanowire Waveguide with Relatively Long Propagation Length

Coupling of incident light through an air region into an S-shape silver (Ag) plasmonic nanowire waveguide (SSAPNW) is a highly difficult challenge of light guiding on the surface of metal nanowire. In this paper, we numerically analyze the coupling effect of an SSAPNW which is covered by a dielectric medium using a finite element method. The coupling effect can be modulated by adjusting the Ag nanowire diameter and the covering dielectric medium width and wavelength of incident light, and the propagation length of surface plasmon (SP) coupling can be maximized. Simulation results reveal that the field confinement can be significantly improved and the majority of the electric field can be carried on the surface of a bending Ag nanowire. The effect of electric field transport along an SSAPNW due to SP coupling and Fabry-Perot resonance is investigated for different dimensions and lengths. Accordingly, long propagation lengths of about 41.5 μm for 10?×?SSAPNW at an incident wavelength of 810 nm and longer propagation length can be achieved if more sections of an SSAPNW are used. Simulation results offer an efficient method for optimizing SP coupling into bending metal nanowire waveguides and promote the realization of highly integrated plasmonic devices.     

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...