Vincent Mathew

Tunable filter using ferroelectric-dielectric periodic multilayer

The microwave optical properties of a photonic crystal-based tunable single and multichannel filter are theoretically investigated using the transfer matrix method, finite difference time domain method, and the plane wave expansion method. By applying an external voltage of 8  V/micron about a 35% frequency tuning is obtained. It is found that the number of transmission peaks is directly proportional to the number of periods (N). In addition to this, the dependence of layer thicknesses, angle of incidence and polarization are also analyzed, and it is noticed that the filtering frequency is invariant in angle and polarization.

Dispersion and Field Distribution of SPP Waves at the Interface of a Metal and Nonlinear Magnetic Material

We study the properties of surface plasmon polaritons at an interface between a metal and a strongly nonlinear magnetic cladding, characterized by permeability

Vortex dynamics effects on microwave propagation in high temperature superconducting coplanar waveguides

\mu=\mu_\textrm{l}+\mu_{\textrm{nl}} H^2

Effect of Counter-doping Thickness on Double-gate MOSFET Characteristics

. It is observed that the dispersion of modes has a significant dependance on the incident power. The incident power can be adjusted to control the propagation length. In addition, the structure shows strong confinement of the modes at the interface.

Computation of flux effects in high temperature superconducting coplanar waveguide

An analysis of the microwave signal propagation through a High Temperature Superconducting (HTS) transmission line should take into account the vortex dynamics effects of the HTS material used for the study. Taking Coplanar Waveguide (CPW) as a model transmission line, we simulated the transmission characteristics using a field computation method based on Galerkins procedure. The vortex effects were incorporated into the study using the surface impedance derived from the modified two-fluid model proposed by Coffey and Clem which takes into account the field and thermal effects in a self consistent manner. The increase of temperature and magnetic field significantly affected the attenuation due to the enhanced vortex motion. The observed dip in the value of attenuation of the transmission line at low field values in high temperature range is explained using the vortex effects. It is found that the dispersion is considerably low for the proposed geometrical structures. Simulations were performed for varyin...

Longitudinal Localized Surface Plasmons in Trimer Nanocylinder System

This paper presents a study of the influence of variation of counter doping thickness on short channel effect in symmetric double-gate (DG) nano MOSFETs. Short channel effects are estimated from the computed values of current-voltage (I-V) characteristics. Two dimensional Quantum transport equations and Poisson equations are used to compute DG MOSFET characteristics. We found that the transconductance (g m ) and the drain conductance (g d ) increase with an increase in p-type counter-doping thickness (T c ). Very high value of transconductance (g m = 38 mS/㎛) is observed at 2.2 ㎚ channel thickness. We have established that the threshold voltage of DG MOSFETs can be tuned by selecting the thickness of counter-doping in such device.

Modeling of frequency response in vortex state of high temperature superconducting microstrip and slotline

We present a simulation methodology of propagation parameters and study their relationship with flux effects in a High Temperature Superconducting (HTS) Coplanar Waveguide placed in an external magnetic field. The impact of vortex dynamics on the electromagnetic signal propagation is clearly made out for a wide range of applied field, temperature and strip thickness. The vortex effects are incorporated by using a complex dynamic mobility term proposed by Coffey and Clem (CC) in their modified two-fluid theory. The dyadic Greens functions in Spectral Domain are formulated accordingly by treating the surface impedance derived from CC model as a complex resistive boundary condition. The thermal and field effects are incorporated into the analysis in a self-consistent manner using CC model. By using the Galerkins procedure, the propagation parameters are computed using Müller root finding method. The inclusion of flux dynamics significantly alter the signal attenuation which, in turn, determines the quality factor. The signal dispersion is kept to a minimum and the relationship between flux effects and the microwave signal propagation is explored.

Modeling of High Temperature Superconducting Coplanar Waveguides for microwave propagation under a magnetic field

We report the near field localized surface plasmon characteristics of triangular system of silver nanocylinders and shell nanocylinders interacting with incident plane wave, studied using finite element method. The trimer nanocylinder system possesses far greater structural tunability than either a single nanorod or a nanoshell, along with much larger local field intensity enhancements and far greater sensitivity. The effect of geometrical as well as material parameters on the longitudinal localized plasmon resonance of the trimer nanosystem was investigated. The results provide insight in to the possible tunability of the localized plasmon modes which could find application in designing of chemical and biological sensors, electron emitters, etc.

Tunable surface plasmon polaritons in metal-strip waveguides with magnetized semiconductor substrates in Voigt configuration

A modeling technique to study the frequency response of electromagnetic signal fed to High Temperature Superconducting (HTS) microstrip and slotline exposed to a constant dc magnetic field is presented. The computation is done for a temperature close to the critical temperature where the vortex effects significantly influence the signal propagation. The flux related effects are modeled using a modified two-fluid theory proposed by Coffey and Clem (CC). The complex penetration depth obtained by CC model is used to derive a complex resistive boundary condition which, in turn, incorporates the HTS effects and modifies the dyadic Greens functions derived for microstrip and slotline using Spectral Domain Method (SDM). The propagation parameters are obtained using Galerkin procedure for a wide range of applied dc field and microwave signal frequency. Both the strip lines are of same geometrical dimensions for a comparative study. Phase constant of the signal varies with signal frequency whereas the attenuation constant is largely influenced by vortex movements. The study presents a comparative modeling method for microstrip and slotline and relates vortex physics with microwave signal propagation for a wide range of applied dc field and signal frequency.

Effect of Gyrotropic Substrates on the Surface Plasmon Polaritons Guided by Metal Films of Finite Width

The microwave propagation through a High Temperature Superconducting (HTS) Coplanar Waveguide (CPW) exposed to a magnetic field is simulated for a wide range of temperature, applied field and transmission line geometry. The magnetic field effects of a HTS coplanar waveguide is studied using the modified two-fluid model proposed by Coffey and Clem (CC). The surface impedance of the high temperature superconducting strip is determined using the CC model. This enters as the complex valued resistive boundary condition and by using the Galerkins procedure, we study the propagation parameters and the unloaded Q value of the coplanar waveguide. The spectral domain dyadic Greens functions for the transmission line are formulated by treating coplanar waveguide as a coupled slotline. The results are in tune with the vortex dynamics explored by CC model. The simulation of transmission characteristics of the coplanar waveguide in the microdimensions shows lower dispersion and attenuation. The variations in signal transmission are explained using the vortex effects.