Search results for "time-domain"

High performance for refractive index sensors via symmetry-protected guided mode resonance.

2021

The symmetry breaking in a typical dielectric GMR-grating structure allows the coupling of the incident wave with the so-called Symmetry-Protected Modes (SPM). In this present work, the excitation conditions of such particular modes are investigated. A parametric study including the grating dimensions is carried out to exploit them for a blood refractive index sensing with higher Sensitivity (S) and Figure Of Merit (FOM). To our knowledge, the performances obtained by FDTD calculations (Q = 2.1 × 104, S = 657 nm/RIU and FOM ≃ ~9 112 RIU−1) and FMM calculations (Q = 3 × 106, S = 656 nm/RIU and FOM ≃ ~1.64 × 106 RIU−1) are the highest level reached.

A finite difference time domain model for the Titan ionosphere Schumann resonances

2007

[1] This paper presents a numerical approach to model the electrical properties of Titan's atmosphere. The finite difference time domain technique is applied to model the atmosphere of Saturn's satellite in order to determine Schumann resonant frequencies and electromagnetic field distributions at the extremely low frequency range. Spherical coordinates are employed, and periodic boundary conditions are implemented in order to exploit the symmetry in rotation of the celestial body. Results are compared with a previous model using the transmission line matrix method up to 180 km altitude. For the first time a numerical FDTD model up to 800 km altitude is carried out, and we report lower freq…

An optical pulse modulator based on an all-fiber mirror

1996

Electrical analogous in viscoelasticity

2014

In this paper, electrical analogous models of fractional hereditary materials are introduced. Based on recent works by the authors, mechanical models of materials viscoelasticity behavior are firstly approached by using fractional mathematical operators. Viscoelastic models have elastic and viscous components which are obtained by combining springs and dashpots. Various arrangements of these elements can be used, and all of these viscoelastic models can be equivalently modeled as electrical circuits, where the spring and dashpot are analogous to the capacitance and resistance, respectively. The proposed models are validated by using modal analysis. Moreover, a comparison with numerical expe…

Transparent Boundary Condition for Oseen-Frank Model. Application for NLC Cells With Patterned Electrodes

2015

In the present work a novel application of Transparent Boundary Conditions (TBC) to nematic liquid crystal cells (NLCC) with planar alignment and a patterned electrode is studied. This device is attracting great interest since it allows soliton steering by optically and externally induced waveguides. We employ the continuum Oseen-Frank theory to find the tilt and twist angle distributions in the cell under the one-constant approximation. The electric field distribution takes into account the whole 2D permittivity tensor for the transverse coordinates. Standard finite difference time domain methods together with an iterative method is applied to find an approximate solution to our coupled pr…

Soil ionization in earth electrodes by a finite difference time domain scheme

2004

This paper proposes a finite difference time domain numerical scheme devoted to analyze the transient behavior of earth electrodes during the soil breakdown that can take place when a surge current has to be drained. To this aim, Maxwell's equations together with a space-time variable resistivity function are used. The model has been validated by comparing the computed results with data available in the technical literature. Simulation results related to complex earth electrodes of limited extension are reported. Electrodes of larger extension can be easily simulated but requiring more computational resources.

Time-Domain Integration of Terahertz pulses

2021

We report on the time-domain integration of terahertz pulses obtained via the tight confinement of the radiation in a tapered two-wire waveguide. Both simulation and experimental results prove the time integration capability of this structure.

Broadband printed dipole with integrated via-hole balun for WiMAX applications

2010

A broadband balanced printed dipole antenna for WiMAX applications (2.5/3.6 GHz) is presented. An integrated via-hole balun is used to feed the antenna and a Yagi-like scheme is proposed to improve the gain. The design has been optimized by means of parametric FDTD simulations. The antenna was fabricated and measured, giving a bandwidth higher than 50% and a gain higher than 4 dBi. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:52–55, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25671

Ultra-broadband terahertz time domain spectroscopy by Solid State Biased Coherent Detection

2017

The spectral fingerprint of ibuprofen within the THz frequency window has been retrieved through an ultra-broadband THz Time Domain Spectrometry set-up. The latter implements the Solid State Biased Coherent Detection scheme, based on a compact CMOS-compatible integrated device. Such a technique shows unprecedented advantages in term of bandwidth (greater than 10 THz) over other solid state methods like electro-optic sampling.

Tapered Two-Wire Waveguide for Time-Domain Integration of Broadband Terahertz Pulses

2021

We show the time-domain integration of terahertz pulses achieved in a sub-wavelength, tapered two-wire waveguide. Both simulation and experimental results prove the time integration functionality of this waveguide topology.