Ultra-Compact High-Speed Electro-Optical Modulator with Extremely Low Energy Consumption Based on Polymer-Filled Hybrid Plasmonic Waveguide

Plasmonics - In this paper, we propose an ultra-compact high-speed electro-optical modulator with extremely low energy consumption based on silicon-polymer-metal hybrid plasmonic waveguide. Spatial...     

Design and Optimization of Open-cladded Plasmonic Waveguides for CMOS Integration on Si3N4 Platform

Herein, we present a design analysis and optimization of open-cladded plasmonic waveguides on a Si₃N₄ photonic waveguide platform targeting CMOS-compatible manufacturing. For this purpose, two design approaches have been followed aiming to efficiently transfer light from the hosting photonic platform to the plasmonic waveguide and vice versa: (i) an in-plane, end-fire coupling configuration based on a thin-film plasmonic structure and (ii) an out-of-plane directional coupling scheme based on a hybrid slot waveguide. A comprehensive numerical study has been conducted, initially deploying gold as the reference metal material for validating the numerical models with already published experimental results, and then aluminum and copper have been investigated for CMOS manufacturing revealing similar performance. To further enhance coupling efficiency from the photonic to the plasmonic part, implementation of plasmonic tapering schemes was examined. After thorough investigation, plasmo-photonic structures with coupling losses per single interface in the order of 1 dB or even in the sub-dB level are proposed, which additionally exhibit increased tolerance to deviations of critical geometrical parameters and enable CMOS-compatible manufacturing.

     

Microring Switching Control Using Plasmonic Ring Resonator Circuits for Super-Channel Use

The multi-wavelength selection and switching system using the hybrid plasmonic add-drop ring resonator (HPARR) for optical communication is proposed for multi-carrier super-channel-based designed. The plasmonic polariton technique applied in the ring resonator mode to the alternate waveguide interferometer switches the multi-wavelength laser emission in the various ranges. The combination of curvature-coupled plasmon ring and substances with different refractive index allows switching the multi-wavelength emission to shorter the free spectrum range (FSR) and specific wavelengths, without an applied pump signal or adjusted the ring size. It is suitable for the super-channel of wavelength division multiplex (WDM) in the future optical network.

     

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.

     

Multilayer Hybrid Plasmonic Nano Patch Antenna

This is the first report of a hybrid plasmonic nano patch antenna having metal insulator metal (HMIM) multilayer configuration. It is designed in a footprint area of 1.7 × 1.175 μm² to resonate at 1.55 μm wavelength. The proposed antenna is inset fed by an HMIM plasmonic waveguide for achieving proper impedance matching. It is observed, through electromagnetic numerical simulation, that the proposed plasmonic nano patch antenna emits a directional beam with a bandwidth, gain, and efficiency of 0.194 μm, 8.3 dB, and 96% respectively, which are significantly higher than previously reported designs. Since inset-fed antennas are suitable for developing high-gain antenna array, hence further, we examined antenna performance by designing antenna array. The proposed antenna is practically realizable and can be fabricated using standard semiconductor fabrication process. Moreover, it could be used for numerous chip scale applications such as wireless interconnects energy harvesting, photoemission, photo detection, scattering, heat transfer, spectroscopy, and optical sensing.

     

Reconfigurable Plasmonic Logic Gates

Reconfigurable one-, two-, and three-bit plasmonic logic gate configurations have been proposed, which work by covering a straight slot waveguide with materials with tunable dielectric constants, such as graphene. By encoding the logic states in the values of dielectric constants as opposed to different waveguides, the plasmon excitation problems are minimized and the simplified logic gate configurations could be easily implemented.

     

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.     

Hybrid Dielectric-Loaded Plasmonic Waveguide-Based Power Splitter and Ring Resonator: Compact Size and High Optical Performance for Nanophotonic Circuits

The key challenge of the plasmonic waveguide is to achieve simultaneously both the long propagation length and high confinement. The hybrid dielectric-loaded plasmonic waveguide consists of a SiO₂ stripe sandwiched between a Si-nanowire and a silver film and thus promises as a best candidate to overcome this challenge. We propose to exploit this unique property of this structure to design different high-efficient silicon-based plasmonic components including waveguide, power splitter, and wavelength-selective ring resonator. As a result, the proposed power splitter with a waveguide cross section (λ ²/60) and a strong mode confinement area (~λ ²/240) features a low power transmission loss (<0.4 dB) at the optimal arm length of 4 μm with respect to different separation distances of output arms. Moreover, we also demonstrate that a plasmonic ring resonator with a compact ring radius of 2 μm may achieve high optical performance such as high-extinction ratio of 30 dB, large free spectral range of 67 nm, and small bandwidth of 0.6 nm. These superior performances make them promising building blocks for integrated nanophotonic circuits.     

Controllable Mode Hybridization and Interaction Within a Plasmonic Cavity Formed by Two Bimetallic Gratings

We theoretically study mode hybridization and interaction among surface plasmon polariton Bloch wave mode, Fabry–Perot cavity mode, and waveguide mode within a plasmonic cavity composed by two parallel planar bimetallic gratings. Four hybridized modes result from mode hybridization between surface plasmon polariton Bloch wave modes on the two gratings are observed. By changing the dielectric environment, mode hybridization behavior can be manipulated. Importantly, waveguide-plasmon polariton mode due to hybridization between grating supported surface plasmon polariton Bloch wave mode and cavity supported waveguide mode is observed. We demonstrate that surface plasmon polariton Bloch wave mode and Fabry–Perot cavity mode with the same mode symmetry can interact by presenting an anticrossing behavior, which can be controlled by laterally shifting one grating with respect to the other that causes a phase difference shift of the two involving modes. The proposed plasmonic cavity offers potentials for subwavelength lithography, tunable plasmonic filter, and controllable light-matter interaction.     

A Sub-wavelength Electro-optic Switch Based on Plasmonic T-Shaped Waveguide

A sub-wavelength electro-optic switch based on plasmonic T-shaped waveguide has been proposed and numerically investigated. The finite-difference time-domain simulation results reveal that the switch based on T-shaped waveguide with two U-shaped grooves can realize the function of switching single wavelength from one port to the other by an external voltage. The U-shaped structure is composed of two teeth filled with highly nonlinear organic EO material and one groove filled with 6H-SiC connecting the two teeth. The switch wavelength can be chosen by adjusting both lengths of the left and right teeth, and the switch voltage is 3.35 V for the wavelength of λ = 730 nm with the insertion loss around −2.6 dB and the extinction ratio around −20 dB at port 2.     

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.     

Ferroelectric Hybrid Plasmonic Waveguide for All-Optical Logic Gate Applications

A ferroelectric hybrid plasmonic waveguide, made of a polycrystal lithium niobate waveguide separated from a gold film by a silicon dioxide isolation layer, is fabricated by use of laser molecular beam epitaxy growth, electron beam evaporation, and focused ion beam etching. Strong subwavelength mode confinement and excellent long-range propagation are achieved simultaneously for the hybrid plasmonic mode. An all-optical logic OR gate is also realized based on the ferroelectric hybrid plasmonic waveguide. This may provide a way for the study of all-optical logic gates and integrated photonic circuits.     

Ultrasmall Plasmonic Cavity for Chemical Sensing

We propose an ultrasmall plasmonic cavity based on the channel waveguides for chemical sensing. The plasmonic mode gap due to cutoff angular frequency enables strong optical confinement in a subwavelength volume and suppression of radiation loss. Due to strong field overlap of the surface plasmon polariton mode with environmental material, large sensitivity (1,100 nm/refractive index unit) and a high figure of merit (330) are achieved in the plasmonic cavity with a small physical size of 600?×?800?×?2,500 nm having a telecommunication resonant wavelength. This plasmonic cavity can introduce a broad range of applications including biochemical sensing and strong light–matter interactions.     

Coupled Plasmonic Cavities on Moire Surfaces

Surface plasmon polariton (SPP) waveguides formed by coupled plasmonic cavities on metallic Moire surfaces have been investigated both experimentally and numerically. The Moire surface, fabricated by interference lithography, contains periodic arrays of one-dimensional cavities. The coupling strength between the cavities has been controlled by changing the periodicities of the Moire surface. The ability to control the coupling strength allows us to tune the dispersion and the group velocity of the plasmonic coupled cavity mode. Reflection measurements and numerical simulation of the array of SPP cavities have shown a coupled resonator type plasmonic waveguide band formation within the band gap. Coupling coefficients of cavities and group velocities of SPPs are calculated for a range of cavity sizes from weakly coupled regime to strongly coupled regime.     

Multi-Directional Plasmonic Splitter and Polarization Analyzer Based on the Catenary Metasurface

Owing to the unique properties of strongly confined and enhanced electric fields, surface plasmon polaritons (SPPs) provide a new platform for the realization of ultracompact plasmonic circuits. However, there are challenges in coupling light into SPPs efficiently and subsequently routing SPPs. Here, we propose a multi-directional SPP splitter and polarization analyzer based on the catenary metasurface. Based on the abundant electromagnetic modes and geometric phase modulation principle of catenary structure, the device has realized high-efficiency beam splitting for four different polarization states (x-polarization, y-polarization, LCP, and RCP). The central wavelength of the device is 632 nm and the operation bandwidth can reach 70 nm (585–655 nm). Based on the phenomenon of SPP beam splitting, we present a prototype of a polarization analyzer, which can detect the polarization state of incident light by adding photodetector with light intensity logic threshold in four directions. Moreover, by combining this device with dynamic polarization modulation techniques, it is possible to be served as a router or switch in integrated photonic circuits.

     

A Design Method for a Micron-Focusing Plasmonic Lens Based on Phase Modulation

A design method of a micron-focusing plasmonic lens is proposed, which consists of a nanoaperture surrounded by concentric annular grooves with fixed width and depth. The phase modulation of the radiation lights decoupled from surface plasmon polariton waves by the annular grooves is realized by altering the radii of the grooves. Based on the principle of the constructive interference, a design formula of a micron-focusing plasmonic lens is deduced. The transmitted fields through the designed plasmonic lenses are numerically simulated with finite-difference time-domain method, and the results show that a circular focusing spot is generated where the focal length can be controlled in several micrometers, which agree with our theoretical analysis.     

High Efficiency Tunable Graphene-Based Plasmonic Filter in the THz Frequency Range

Plasmonics - A tunable plasmonic filter waveguide with indium antimonide activated by graphene layer configuration is proposed and numerically investigated. We demonstrate that the proposed tunable...     

Portable Capillary Sensor Integrated with Plasmonic Platform for Monitoring Water Pollutants

In this work, a label-free and inexpensive method for the monitoring of water pollutants is demonstrated. We introduce a localized surface plasmon resonance (LSPR) based plasmonic capillary optical biosensor to detect microalgae cells. Here, the plasmonic capillary biosensor was prepared by decorating the inner walls of a glass capillary with gold nanoparticles that were employed for investigations. Since the gold nanoparticle has the potential to sense pollutants in water rapidly with high sensitivity and they are expected to perform a significant role in environmental monitoring. Our proposed plasmonic capillary sensor has a detection limit of 25 algal cells (Chlorella sp. CB4). Furthermore, the plasmonic capillary sensing platform significantly simplifies sensor fabrication and reduces the cost of the device. We believe that the presented plasmonic sensor could stand as a potential candidate for developing a cost-effective, label-free, and rapid sensing platform to detect microalgae pollutants present in the water at very low concentrations.

     

Theoretical Investigation of an Interferometer-type Plasmonic Biosensor Using a Metal-insulator-silicon Waveguide

This work proposes and investigates theoretically a biosensor that is an integrated plasmonic Mach–Zehnder interferometer. The biosensor consists of three sections. The first and third sections are input and output dielectric waveguides whose core is a silicon film. The second section is a combination of a surface plasmon polariton waveguide and a metal-insulator-silicon waveguide, which are separated by a thick gold film. The former and the latter function as sensing and reference arms, respectively. The latter supports a mode whose fields are highly enhanced in a thin insulator, silicon nitride film, and it has relatively small propagation loss. It is shown that the biosensor has insertion loss lower than 2 dB, and that it is very compact since the length of its second section for sensing is shorter than 6 μm. In addition, it is discussed that it can be easily implemented by using simple fabrication processes. Analyzed are the characteristics of sensing a refractive index change of liquid covering the biosensor. Despite its compactness, they are similar to those of previous surface plasmon interferometers. Also, its characteristics as a DNA sensor are analyzed. The analysis demonstrates that the biosensor can detect sensitively target single-stranded DNAs whose total weight is smaller than 10 fg.     

Nanoscale Surface Plasmon All-Optical Diode Based on Plasmonic Slot Waveguides

A nanoscale surface plasmon all-optical diode is proposed based on a plasmonic slot waveguide having an asymmetric plasmonic grating in the center. The asymmetric configuration of the plasmonic grating and the unique dispersion relations of the plasmonic slot waveguide ensure the nonreciprocal transmission properties. High transmittance contrast ratio of 1,150 is achieved theoretically. The performance of the surface plasmon all-optical diode does not have any high power requirement. This may open a new way for the study of integrated photonic devices based on surface plasmons.