FDTD Solutions (für Windows und Linux Systeme) ermöglicht die kostengünstiges, hocheffizientes Prototyping von Mikro- und Nanooptik mit der bewährten. Während viele elektromagnetische Simulationstechniken im Frequenzbereich angewendet werden, löst FDTD die Maxwell-Gleichungen im Zeitbereich. Das. In this thesis, new possibilities will be presented how one of the most frequently used method - the Finite Difference Time Domain method (FDTD) - can be.
FDTD SolutionsFinite-difference time-domain method (FDTD) is widely used for modeling of computational electrodynamics by numerically solving Maxwell's equations. Introduction to the Finite-Difference Time-Domain (FDTD) Method for Electromagne (Synthesis Lectures on Computational Electromagnetics, Band 27) | Gedney. Numerische Feldberechnungsverfahren, so auch FDTD sind in der Lage, bei einer vorgegebenen Einspeisung und gegebener Struktur des Applikators mit.
Fdtd 2. PML and dispersive materials VideoLecture 6 (FDTD) -- Implementation of 1D FDTD
The finite-difference time-domain FDTD method is used to solve Maxwell's equations in the time domain. The equations are solved numerically on a discrete grid in both space and time, and derivatives are handled with finite differences.
It does not make any approximations or assumptions about the system and, as a result, it is highly versatile and accurate.
Since it solves for all vector components of the electric and magnetic fields, it is a fully-vectorial simulation method.
Because it is a time domain method, FDTD can be used to calculate broadband results from a single simulation. FDTD is typically used when the feature size is on the order of the wavelength.
This wavelength scale regime where diffraction, interference, coherence and other similar effects play a critical role is called wave optics. In the case of TE, the location of the fields in the mesh is shown in Figure 2.
Figure 2: Location of the TE fields in the computational domain. The TE fields stencil can be explained as follows.
The E y field locations coincide with the mesh nodes given in Figure 1. In Figure 2, the solid lines represent the mesh given in Figure 1.
The E y field is considered to be the center of the FDTD space cell. The dashed lines form the FDTD cells.
The magnetic fields H x and H z are associated with cell edges. The locations of the electric fields are associated with integer values of the indices i and k.
The numerical analog in Equation 1 can be derived from the following relation:. The sampling in space is on a sub-wavelength scale.
The time step is determined by the Courant limit:. The location of the TM fields in the computational domain follows the same philosophy and is shown in Figure 3.
Figure 3: Location of the TM fields in the computational domain. Nonlinearity and Anisotropy Simulate devices fabricated with nonlinear materials or materials with spatially varying anisotropy.
Choose from a wide range of nonlinear, negative index, and gain models Define new material models with flexible material plug-ins.
Powerful Post-Processing Powerful post-processing capability, including far-field projection, band structure analysis, bidirectional scattering distribution function BSDF generation, Q-factor analysis, and charge generation rate.
Automation FDTD is interoperable with all Lumerical tools through the Lumerical scripting language, Automation API, and Python and MATLAB APIs.
Build, run, and control simulations across multiple tools. Use a single file to run optical, thermal, and electrical simulations before post-processing the data in MATLAB.
Want to know more about FDTD? Ready for a quote? Iterating the E-field and H-field updates results in a marching-in-time process wherein sampled-data analogs of the continuous electromagnetic waves under consideration propagate in a numerical grid stored in the computer memory.
This description holds true for 1-D, 2-D, and 3-D FDTD techniques. When multiple dimensions are considered, calculating the numerical curl can become complicated.
Kane Yee's seminal paper proposed spatially staggering the vector components of the E-field and H-field about rectangular unit cells of a Cartesian computational grid so that each E-field vector component is located midway between a pair of H-field vector components, and conversely.
Furthermore, Yee proposed a leapfrog scheme for marching in time wherein the E-field and H-field updates are staggered so that E-field updates are conducted midway during each time-step between successive H-field updates, and conversely.
On the minus side, this scheme mandates an upper bound on the time-step to ensure numerical stability. To implement an FDTD solution of Maxwell's equations, a computational domain must first be established.
The computational domain is simply the physical region over which the simulation will be performed. The E and H fields are determined at every point in space within that computational domain.
The material of each cell within the computational domain must be specified. Typically, the material is either free-space air , metal , or dielectric.
Any material can be used as long as the permeability , permittivity , and conductivity are specified. The permittivity of dispersive materials in tabular form cannot be directly substituted into the FDTD scheme.
Instead, it can be approximated using multiple Debye, Drude, Lorentz or critical point terms. This approximation can be obtained using open fitting programs  and does not necessarily have physical meaning.
Once the computational domain and the grid materials are established, a source is specified. The source can be current on a wire, applied electric field or impinging plane wave.
In the last case FDTD can be used to simulate light scattering from arbitrary shaped objects, planar periodic structures at various incident angles,   and photonic band structure of infinite periodic structures.
Since the E and H fields are determined directly, the output of the simulation is usually the E or H field at a point or a series of points within the computational domain.
The simulation evolves the E and H fields forward in time. Processing may be done on the E and H fields returned by the simulation.
Data processing may also occur while the simulation is ongoing. The most commonly used grid truncation techniques for open-region FDTD modeling problems are the Mur absorbing boundary condition ABC ,  the Liao ABC,  and various perfectly matched layer PML formulations.
However, PML which is technically an absorbing region rather than a boundary condition per se can provide orders-of-magnitude lower reflections.
The PML concept was introduced by J. Berenger in a seminal paper in the Journal of Computational Physics. The latter two PML formulations have increased ability to absorb evanescent waves, and therefore can in principle be placed closer to a simulated scattering or radiating structure than Berenger's original formulation.
To reduce undesired numerical reflection from the PML additional back absorbing layers technique can be used.
Notwithstanding both the general increase in academic publication throughput during the same period and the overall expansion of interest in all Computational electromagnetics CEM techniques, there are seven primary reasons for the tremendous expansion of interest in FDTD computational solution approaches for Maxwell's equations:.
Taflove has argued that these factors combine to suggest that FDTD will remain one of the dominant computational electrodynamics techniques as well as potentially other multiphysics problems.
There are hundreds of simulation tools e. OmniSim, XFdtd, Lumerical, CST Studio Suite, OptiFDTD etc.
Frederick Moxley suggests further applications with computational quantum mechanics and simulations. The following article in Nature Milestones: Photons illustrates the historical significance of the FDTD method as related to Maxwell's equations:.
Allen Taflove's interview, "Numerical Solution," in the January focus issue of Nature Photonics honoring the th anniversary of the publication of Maxwell's equations.
This interview touches on how the development of FDTD ties into the century and one-half history of Maxwell's theory of electrodynamics:.
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