Search

In this paper, a novel structure based on nanodisk and nanoring resonators in a Metal-Insulator-Metal (MIM) plasmonic waveguide for triple-channel wavelength demultiplexer (WDM) is proposed. WDM structure consists of a bus waveguide which has been perpendicularly coupled with several nanodisks and nanorings and three drop waveguides. The proposed structure can be adjusted by appropriate choose of refractive index and geometrical parameters. The simulation results present that the transmission spectrum efficiency in the proposed structure increases up to about 80%. The proposed structure can be used in the ultra-compact demultiplexer devices, nanosensors and optical integrated circuits. In this paper, the used numerical method is two dimensional Finite-Difference Time-Domain (FDTD) approach.

The key point of improving the thermal conductivity of polymer is to increase the orientation of the chains and reduce the disorder conformation. Recently, the nanoring structures are incorporated into polymers to tune the chain dynamics. In this work, the wide diameter (4~7 nm) but short length (~10 nm) BN nantube as nanoring incorporated into polyethylene. The thermal conductivity of nanocomposite can be increased by about 3 times from the nonequilibrium molecular dynamics calculation. Structurally, the polyethylene chains are aligned along the nanoring. In addition, the confinement of nanoring reduces the mobility of polyethylene chains by 40% and enhances the interatomic and interaction, which results in red shift of low frequency phonons. The results provide valuable guidance for improving the thermal conductivity of polymers by doping nanoring.

In this paper, we report on the theoretical and numerical study of the transmission of circularly polarized vortex beams through a plasmonic coaxial nanoring. We show that the transmission peak wavelength of an incident circularly polarized vortex beam is dominantly governed by the total angular momentum, which determines the coupling to the plasmonic eigenmode supported by the coaxial nanoring with a given geometry and ultimately the transmitted beam in the far field. In addition, our study shows that the total angular momentum of the incident circularly polarized vortex beam can be conserved, where the far field of the transmitted beam contains both left- and right-handed circular polarization components with correspondingly modulated orbital angular momentum preserving the same total angular momentum. Our work can be potentially useful to advanced nanophotonic devices harnessing light's angular momentum division.

The purpose of this project is to visualize and study the electronic properties of carbon nanostructures. The principal structures studied are AA and AB (Bernal) stacked graphene bilayers, an 80C nanocone with pentagonal defects at its apex, and a 16C nanoring. Graphene and other based nanostructures have attracted much attention due to their unique electronic properties. For example, bilayer graphene shows superconductivity at certain magic angles of rotation. Open source molecular modeling and visualization programs like SAMSON, Avogadro, and VMD are utilized to generate the structures above. Using bond information in order to find nearest neighbors, an adjacency matrix can be generated from which the energy eigenvalues are solvable and are used to visualize the dispersion relation, free energy, persistent current, Green’s function, and entanglement entropy. The goal of this project is to study the effect of rotation on the electronic properties of bilayer graphene, particularly as it pertains to the magic angle where superconductivity occurs, as well as the electronic properties of the bilayer Moire patterns which emerge due to the superposition of the identical lattices at different angles. An important goal is to incorporate phonon interactions into the tight-binding model for carbon structures, and to utilize quantum based computing as a tool to find the ground state properties of these structures, particularly in the terminating case where boundary conditions have an effect.

We propose complete technology-design-system co-optimization method in which power, performance, thermal, area and cost metrics are all simultaneously optimized from transistor to mobile SOC system level. This novel method, Unified Technology Optimization Platform using Integrated Analysis (UTOPIA), incorporates thermally limited performance, wafer process complexity and die area scaling model in addition to author's previous transistor-interconnect optimization method. Proposed UTOPIA is applied evaluating novel alternative transistor architectures. Two novel transistor architectures, Hexagonal NanoWire (HNW) and NanoRing (NR), are proposed and demonstrated with improved SCEs, higher drive current and lower parasitic capacitance compared to conventional FinFET, Nanowire (NW) or Nanoslab (NS).

Metallic nanoparticles shows interesting optical response because of the phenomena of localized surface plasmon resonance (LSPR) in it. These LSPR modes of metallic nanoparticles always have sub-wavelength features which are considered to be useful in the design of highly compact optical devices. But in many previous works, the optical response of these nanoparticles (single or mass) are collected through free space coupling into spectrometers or other instruments, which is still in a macro style. Recently, some researchers studied the optical properties of silicon waveguides with metallic nanoparticles embedded in it, in order to construct high performance optical components with a highly compact volume. The nanoparticles are always embedded inside the waveguide or located in a gap cut cross the waveguide to enhance the light-nanoparticle interaction as optical energy is mainly concentrate inside the silicon core. However, this will make the fabrication process more complex and rise up the fabrication cost, besides, the cut of the waveguide will cause extra energy loss unavoidably. In this paper, we numerically study the excitation of LSPR mode of metallic nanoparticles loaded on the waveguide surface, which is much easier for fabrications compare with those works where nanoparticles are embedded inside or located in a gap cut cross the waveguide. By examine the interaction of nanoparticles (nano split-rings, nano-strips) with different waveguide modes, we show how to efficiently excite the LSPR mode about a metallic nanoparticle which located on the surface of a silicon waveguide. Besides, through further analysis, we found that metallic nanoring loaded on silicon waveguide exhibits richer optical response, by carefully choosing the geometry parameters of both the ring and the waveguide. These findings may provide new ideas in designing of hybrid nanoparticle-waveguide system to construct highly compact devices for optical communications, optical sensing, and other areas.

Spin-transfer torque magnetic random access memory (STT-MRAM) is a prospective candidate for cache and main memory designs. However, the reliable revision of magnetization using current requires high current density, which is hardly affordable in aggressive scaling-down technology node. Nanoring shaped magnetic tunneling junction (NR-MTJ) remarkably reduces STT programming current density, as indicated by theoretical analysis. In this paper, we first introduce the fundamental of STT technology and describe the NR-MTJ's structure and characteristics. The design and implementation of a 4Kb STTMRAM with NR-MTJs, and a TCAM design for high speed and robustness are then demonstrated.

We design and simulate a simple plasmonic absorber by employing a three-layer structure comprised of square nanoring array on top of the dielectric subtract followed by a gold reflector. To achieve near perfect absorption, several configurations of the top layer (plasmonic nanoparticle) are proposed, which includes a gold nanoring, horizontally split ring, vertically split ring and quad-split ring, respectively. Simulation results indicate that for some geometries, dual broad absorption bands with absorption efficiencies greater than 99% are obtained, which is highly suitable for solar cell applications.

Trapping and detection of micro- and nano-objects at low incident laser powers in the near-infrared region (NIR) is crucial for many biological applications [1]. Using a conventional optical tweezer method, trapping is limited to dielectric particles larger than 100nm in size with high incident laser powers. For this reason, plasmonic nanostructures, which have recently attracted research attentions, offered enhanced trapping fields at their resonant wavelengths, and subsequently can be used to trap and detect silica dielectric particles down to 12nm and single 3.4nm bovine serum albumin proteins using low incident powers (< 1mW) [2].

Simulation of GaAs nanorings formation by droplet epitaxy was carried out using a kinetic lattice Monte Carlo model. Dependence of nanoring morphology on growth temperature, arsenic flux intensity and gallium drop surface density was demonstrated. The formation conditions for single, double and triple concentric rings were analyzed.

A high tunable terahertz graphene-based absorber which can operate in three band is presented. A patterned sheet with an array of graphene nano-disc can enhance absorption at the single resonance frequency. By insertion of five graphene discs in one unit cell, the performance of this absorber is improved. The five nano-discs have designed with different sizes for achieving multi-band operation. The effects of the radius and distance between the discs are studied. Good absorption, compact size and operation at the THz band are the major advantages of the introduced structure. Also the tunability is more than the state in which graphene based nano-disc, nano-ribbon, nanoring or cross-shaped is utilized.

We theoretically and experimentally show that a subwavelength plasmonic ring consisting of four gold nanoparticles can support strong artificial magnetism and magnetic-based Fano resonances at optical frequencies. This is achieved through controlled symmetry breaking of the nanoring geometry, which induces tailored interference between electric and magnetic plasmon modes supported by the nanocluster, leading to enhanced optical magnetism and a distinctively sharp Fano response in the scattering spectrum. These results pave the way to building blocks for negative-index metamaterials and novel single-molecule, magnetic-based biosensors.

We investigate the optical properties and biosensing of gold elliptical nanoring (ENR) arrays with various aspect ratios. Gold ENRs with 1.58 high aspect ratio show a total wavelength shift of 35 nm for molecule sensing.

Coaxial structures are extremely crucial for investigations on surface plasmons since they exhibit special optical properties compared with apertures with other shapes. Different from the traditional extraordinary optical transmission (EOT) observed from nanohole arrays, these ring-like structures can excite cylindrical surface plasmon and planar surface plasmon simultaneously. The nanoring cavities can act as Fabry-Perot resonators, giving rise to coupling between different modes. Importantly, these nanorings have found promising applications in fabricating color filters. Moreover, these coaxial structures are compatible with liquid crystal display techniques, leading to actively tunable optical devices which may be broadly applied in nanophotonics and integrated optics.

Optical transmission properties of periodic gold nanoring arrays fabricated on a free-standing silicon nitride membrane have been investigated experimentally and numerically. The transmission dips caused by the localized surface plasmon resonance (LSPR) are observed and the simulated results show pretty good agreement with the experimental data. The analysis of the electric field distributions indicates the existence of symmetric bonding modes and asymmetric anti-bonding modes of LSPR in the gold nanoring arrays. In addition, the electric field may be enhanced not only at the center of the gold nanorings but also in the spaces between the rings. Moreover, a transition from the anti-bonding mode to bonding mode is achieved by increasing the thickness of the ring. This phenomenon could be interpreted by the effect of linewidth-thickness ratio successfully. These properties may provide valuable and promising applications of advanced LSPR optical devices.

Numerical and fabrication investigations of gold nanoring finite arrays are presented. Surface plasmon resonances are computed using the method of moment surface integral equation. The nanoring arrays are fabrication via electron beam lithography templating and electroless gold plating. The results show the change of surface plasmons resonances, to larger wavelengths, when the nanoring thickness decreases. Also, the array size and the separation distance factors influence the amplitude of the extinction coefficients along with the resonance wavelength.

Summary form only given. Due to their small mode volume, photonic crystal nanocavities are an ideal tool to study enhanced light-matter interactions. As the cavity resonance and Q-factor will change under the influence of objects brought into its evanescent field, the cavity can be used to measure the polarizability of those objects. We show for the first time that a photonic crystal nanocavities, can even be used to measure the magnetic polarizability of a metal nanoring. This is the first measurement of magnetic light-matter interaction at optical frequencies.

Distributed nanopiezoelectric energy harvesting mechanism of ZnO piezoelectric nanorings laminated with distributed electrode segments is analyzed and evaluated in this study. Different from voltage generation mechanism of elastic rings laminated with piezoelectric sensor patches evaluated before, only the membrane strain contributes to the signal and energy generations of the ZnO nanorings. In case studies, voltage signal and generated energy distributions with different segment sizes and nanoring radii are evaluated and analyzed. The fact that the generated signals and energies can be averaged and cancelled out on the electrode segments reduces the total signal and energy. Thus, the total energy generation reduces to zero in the Δψ=30° case with mode number n=6 due to signal cancellations. Based on these analyses and results, optimal distributions of electrode patches to finally achieve highest energy harvesting efficiency for practical applications are also proposed.

Au nanoring solutions of ∼1300 nm in localized surface plasmon resonance wavelength are fabricated and characterized. Their functions of image contrast enhancement in optical coherence tomography (OCT) and photothermal effect are demonstrated. Also, they are delivered into mouse liver for tracking their diffusion in the sample through continuous OCT scanning.

Exchange bias effects have been systematically investigated in Co (25 nm)/CoO (5 nm)/Cu (2 nm) nanoring arrays and Cu (10 nm)/NiFe (30 nm)/IrMn (30 nm)/Cu (2 nm) nanoscale antidot arrays. For the nanorings, the magnetization reversal mechanism and magnitude of exchange bias field He is strongly dependent on the strength and orientation of the cooling field relative to the major axis of the nanorings. The antidot arrays exhibit asymmetric hysteresis loops and show larger He values as compared to the continuous film. This is attributed to reduced interactions in the NiFe layer and constraints imposed on the IrMn domain size by the antidots.

By applying pulsed signals on two point of a quantum nanoring with phase difference Phi, the induced current is calculated theoretically. The method is based on defining all the operators in the Hilbert space of side band states defined in terms of Floquet theorem. Using this method, we have calculated the electronic transport as a function of phase difference of applied signals. It is shown that for special phase difference the polarity of induced current is changed.

An optical biosensor based on gold nanohole arrays was developed using a new nanosphere lithography technique. A vertical deposition method was used to deposit multilayers of a polystyrene (PS) - gold composite on a silanized glass substrate. The SEM images have shown that the gold nanohole and nanoring arrays are distributed uniformly on the substrate. The sensitivity of the gold surface plasmon resonance (SPR) band to the environment was found to be dependent on the geometry of the array. The new nanostructures have been used as platforms for rapid screening of biomolecular interactions. Fibrinogen and biotin absorption studies conducted with the functionalized gold nanostructures demonstrated the feasibility of using them to monitor biomolecular interactions. The sensitivity was found to be around 300 nmldrRIU-1, which is adequate for biosensing applications. The present technique has the advantage of simplicity; the structures can be prepared without any special equipment and a standard cell can be used for optical measurements.

We compare the ultrafast optical response of a nanoring using the semiconductor Bloch equations and our excitonic equations, where phase space filling is included. We demonstrate the potential advantages of the excitonic approach.

Self-assembled single-crystal nanorings (NRs), as small as 10 nm, on Si and Si-Ge alloys have been fabricated by the mediation of Au nanodots. Si-Ge thin films were transformed into Si-Ge nanorings (silicon nanorings doped with controlled amount of Ge) with the assistance of Au catalysts deposited directly onto the thin film with a simple process. The mechanism of nanoring formation involves the mediation by Au nanodots and evaporation of Au-Si (Au-Si-Ge) eutectic liquid droplets at high temperatures. The process promises to be an effective nanofabrication technique to produce high density and uniform in size Si and Si-Ge nanorings.

Based on self-scrolling of Si/Cr bilayer films on Si(001) wafers, various micro- and nanostructures including micro-claws, microtubes, helical nanobelts, nanorings and nanospirals are fabricated in a controllable way. The scrolling principles of the structures from Si/Cr bilayer films are discussed. The flexibility of individual Si/Cr nanospirals and nanorings has been investigated using a nanorobotic manipulator. It has been found that multiple-turn Si/Cr nanorings exhibit a "sticky force" between neighboring bilayers which is mainly attributed to the van der Waals force. Thus, multiple-turn Si/Cr or SiGe/Si/Cr tubes are self-closing and may be used as pipes for micro-fluidics. Moreover, the excellent elasticity and shape-memory effect of these structures may also be utilized for building MEMS/NEMS devices

We experimentally demonstrate that elevating polarization-insensitive nanoring antennas on nanopedestals enables high surface enhanced infrared absorption (SEIRA) signals. This is due to larger and accessible nearfields offering better overlap with biomolecules.