T-shaped Waveguide Research Articles

THE COMPARING OF ACOUSTIC PHONON TRANSPORT ABOUT MONOCHROMATIC MODE AND MIXING MODE THROUGH A DOUBLE T-SHAPED QUANTUM WAVEGUIDE

We compare the thermal conductance of SH mode and mixing mode of acoustic phonons in a double T-shaped quantum waveguide at low enough temperatures by using the scattering-matrix method, and analyze the influence from mode conversion. Our results show that the small changes of the geometric parameters can induce different variation on the thermal conductivity, where the effect of the stub height of SH wave is the strongest. Moreover, the mode conversion plays an important role on the thermal conductivity, especially at the higher temperatures, and the coupling effect between two stubs at mixing mode is larger than that at single SH mode.

Symmetry breaking in a T-shaped photonic waveguide coupled with two identical nonlinear cavities

We consider light transmission in a T-shaped photonic waveguide coupled with two identical symmetrically positioned nonlinear microcavities. We present two types of symmetry breaking. The first one is a result of mixing of the symmetric input wave with antisymmetric bound states in the Fabry-P\'erot interferometer architecture. Similarly, the second mechanism of the symmetry breaking is the result of mixing the symmetrical input wave with the antibonding bound state in a straight waveguide coupled with two cavities positioned perpendicular to the waveguide. In both cases the mixing is due to nonlinearity. In turn, the symmetry-breaking solutions give rise to nonsymmetrical outputs in the T-shape waveguide. These effects are directly demonstrated by the electromagnetic field solutions which are complimented by coupled mode theory for the light transmission.

Spin polarization and charge transmission for a waveguide on surface of topological insulator

We study the spatial distribution of spin polarization and charge transmission for a T-shaped waveguide formed by gate electrodes on the surface of three-dimensional (3D) topological insulator (TI). We demonstrate that an energy gap depending on waveguide geometry parameters is opened and the spin surface-locking is broken by the electrical confinement on the surface of 3D TI. Using continuous condition for the wavefunctions at boundaries between different regions to determine the scattering coefficients, we find that the waveguide can provide an in-plane spin-polarized electron output. This interesting finding may be useful in further understanding surface states of 3D TI.

A simple broadband T-shaped waveguide branch in photonic crystals

A simple broadband T-shaped waveguide branch in photonic crystals is constructed only by introducing three dielectric rods into the waveguide channels near branch region. Numerical results indicate that the bandwidth of high transmission (the total transmittance is larger than 95%) is over 415 nm centered at 1550 nm. Owing to its simple structure and broad enough bandwidth, this waveguide branch is expected to be applied to highly dense photonic integrated circuits.

Double-Teeth-Shaped Plasmonic Waveguide Electro-Optical Switches

An electro-optical switch based on a plasmonic T-shaped waveguide structure with a double-teeth-shaped waveguide filled with 4-dimethylamino-N-methyl-4-stilbazolium tosylate is proposed and numerically investigated. The Finite-difference time domain simulation results reveal that the structure can operate as a circuit switch by controlling the external voltages V1 and/or V2. The proposed structure can also operate as a variable optical attenuator, which can continuously attenuate tie power of a light beam from 6 dB to 30 dB by an external electrical field. The structure is of small size of a few hundred nanometers. Our results may open a possibility to construct nanoscale high-density photonic integration circuits.

Switching through symmetry breaking for transmission in a T-shaped photonic waveguidecoupled with two identical nonlinear micro-cavities

Using coupled mode theory we consider transmission in a T-shaped waveguide coupled withtwo identical symmetrically positioned nonlinear micro-cavities with mirror symmetry. Forinput power injected into the central waveguide we show the existence of a symmetrybreaking solution which is a result of mixing of the symmetrical input wave with anantisymmetric standing wave in the Fabry–Pérot interferometer. With growth of the inputpower, a feature in the form of loops arises in the solution which originates from bistabilityin the transmission in the output left/right waveguide coupled with the first/secondnonlinear cavity. The domains of stability of the solution are found. The breaking of mirrorsymmetry gives rise to nonsymmetrical left and right outputs. We demonstrate thatthis phenomenon can be explored for all-optical switching of light transmissionfrom the left output waveguide to the right one by application of input pulses.

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.

Calculation of characteristics of trapped modes in T-shaped waveguides

The spectrum of the Dirichlet problem for the Laplace operator in a plane T-shaped waveguide is investigated. The critical width of the half-strip branch is determined such that, if the width is greater, the waveguide has no discrete spectrum. The existence of a critical width is proved theoretically.

A nanometeric plasmonic wavelength demultiplexer based on a T-shaped waveguide structure with double teeth-shaped waveguide at telecommunication wavelengths

Characteristics of single tooth-shaped and T-shaped waveguide structures are analyzed. A nanometeric plasmonic wavelength demultiplexer based on a T-shaped waveguide consisting of double rectangular teeth is proposed and numerically simulated by using the finite difference time domain method with a perfectly matched layer absorbing boundary condition. It is found that the new waveguide structure can realize a wavelength demultiplexing function at telecommunication wavelengths. The demultiplexing wavelength can be linearly and independently controlled through the depth of one of the teeth.

Trapped modes in a T-shaped waveguide

We study the discrete spectrum of the Laplace operator with the Dirichlet boundary conditions in a plane waveguide made of a band of unit width and half-band of width h perpendicular to it. The existence of critical width h* ∈ (1,2] is established: in the case of h ∈ (0, h*), the discrete spectrum σdh of the problem contains only one eigenvalur λ1h, but σdh = ⊘ at h ≥ h*. The asymptotics of the eigenvalue λ1h at h → + 0 is found.

Slot waveguide-based splitters for broadband terahertz radiation

We demonstrate a slot waveguide-based splitter for broadband terahertz (THz) radiation using a T-shaped waveguide structure. The structure consists of a fixed-width input waveguide and variable-width output waveguides. We experimentally measure and numerically simulate the THz transmission and reflection properties as a function of the output waveguide width and show that a transmission line model can effectively describe the observations. Based on the high degree of agreement between the experimental results, numerical simulations and the model, we infer the optimal waveguide parameters. The device structure offers new possibilities in designing compact THz devices.

Unidirectional manipulation of surface plasmon polariton by dual-nanocavity in a T-shaped waveguide

A structure of two dimensional T-shaped metal–insulator–metal waveguide with dual-nanocavity is proposed. The two nanocavities located at each side of the slit on the lower metallic surface, act as band rejection filters and are capable of stopping the surface plasmon polaritons (SPPs) at the resonant wavelengths. The Fabry–Perot interferometry theory and the Finite-Difference–Time–Domain method are utilized to investigate the proposed waveguide. The numerical results demonstrate the realization of miniaturized photonic devices for effectively switching the SPPs propagation between the left and right waveguides in one direction.

R-matrix theory with Dirichlet boundary conditions for integrable electron waveguides

R-matrix theory is used to compute transmission properties of a T-shaped electron waveguide and an electron waveguide-based rotation gate by using Dirichlet boundary conditions for reaction region basis states, even at interfaces with external leads. Such boundary conditions have been known to cause R-matrix convergence problems. We show that an R-matrix obtained using Dirichlet boundary conditions can be convergent for some cases. We also show that R-matrix theory can efficiently reproduce results that were obtained using far more computationally demanding methods such as mode matching techniques, tight-binding Green's function methods or the finite element methods.

Novel Optical Neuronal Cell and Data Recognition-generation Circuits in RFID Tags

The optical neuronal cell composed of silicon structure is also studied, and novel cell is proposed. The circuits that recognizes tag call signal and generates the sending data using the analog threshold element with a nonlinear characteristic are studied. In addition, single-mode silicon optical switch with T-shaped SiO2 optical waveguide as a control gate is proposed (5). In this report, the neuronal cell composed of silicon waveguide and electronic active elements is studied, and novel neuronal cell is proposed. The electron-hole pairs generated by illumination with short-wavelength light are used here.

Linear and Non-Linear Response in T-Shaped Electron Waveguides

Recent experimental results on three-terminal ballistic junction (TBJ) [1] showed their interesting electron transport properties as candidates for effective logic gates for quantum computing [2]. A similar device was proposed by Baranger [3] where T-shaped ballistic junction and four-terminal devices were examined. It was shown that oscillatory behavior of transmission coefficients can be explained accurately by bend resistance and threshold effect. In addition for specific parameters he observed appearance of the Wigner cusp [4] in transmission coefficients. In this paper we will show that the Wigner singularities can be observed in measurable quantities, such as conductance and voltage.

Resonance and Antiresonance in Electronic Transport Process Through a T-Shaped Quantum Waveguide

By means of the transfer matrix approach, the linear conductance spectrum for electronic transport through a T-shaped quantum waveguide is calculated. The resonant peaks and the antiresonant dips in the conductance spectrum are mainly focused. The previous prediction about their positions by other theoretical approaches is checked. In addition, a function of spin filtering is suggested based on the interplay of the resonance and antiresonance in this T-shaped quantum waveguide.

Transport of electrons through an asymmetric T-shaped quantum waveguide in a magnetic field

We investigate transport properties of electrons through an asymmetric T-shaped magnetic quantum structure by the mode-mathcing technique and solution of the single electron Schrdinger equation. The results show that the changes of structural factors and magnetic field affect the electron scattering behavior and result in various patterns of electron transmission. When different magnetic configurations and structural factors are used, the transmission exhibits various patterns such as wide valley, sharp peak, resonant reflection, resonant transmission, and so on. Our results show that one may control the transmission property to design interferential quantum devices by adjusting magnetic configurations and or structural parameters.

Tunable T-Shaped Waveguide in Two Dimensional Photonic Crystals Based on Liquid Crystals

In the last years, in order to achieve active tuning of photonic crystals devices, the possibility to use liquid crystal inside photonic crystals has been explored. On this line of argument, in this paper, we numerically investigate a tunable T-shaped waveguide diplexer, based on a two-dimensional square lattice photonic crystal composed of silicon rods in a liquid crystals. We prove that complete splitting of the entire input wavelengths range in two sub-ranges symmetrical with respect to the middle (switching) wavelength, and propagating in right and left arms respectively, can be achieved. Moreover, changing the refractive index of liquid crystals by electro-optical effect, a tuning of switching wavelength of about 60 nm can be obtained.

Investigation of a tunable T-shaped waveguide based on a silicon 2D photonic crystal

We investigate the tunability of a T-shaped waveguiding diplexer, based on a two-dimensional square lattice photonic crystal (PhC) composed of silicon rods in air and in liquid crystals (LCs), respectively. For both devices we prove that a complete splitting of the entire input wavelength range into right and left arms respectively can be achieved. Moreover, a tuning of the switching wavelength can be obtained by changing the refractive index of silicon by the thermo-optic effect for PhCs in air, and the refractive index of liquid crystals by the electro-optic effect for PhCs in LCs.

Active Photonic Crystals Based multiplexer

ABSTRACTIn the last years, in order to achieve active tuning of photonic crystals devices, the possibility to use liquid crystal inside photonic crystals has been explored.On this line of argument, in this paper, we numerically investigate a tunable T-shaped waveguide diplexer, based on a two-dimensional square lattice photonic crystal composed of silicon rods in a liquid crystals. We prove that complete splitting of the entire input wavelengths range in two sub-ranges symmetrical with respect to the middle (switching) wavelength, and propagating in right and left arms respectively, can be achieved. Moreover, changing the refractive index of liquid crystals by electro-optical effect, a tuning of switching wavelength of about 60 nm can be obtained.