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|All versions|{{download|http://www.emagtech.com|EM.Tempo Lesson 11|[[EM.Cube]] 14.10}} }}

In this tutorial you will learn how to use Gaussian beam sources and dispersive material blocks. You will also generate a fixed-cell mesh for your project and set up time-domain field [[animation]].

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! Center Frequency

Open the FDTD Engine Settings dialog from inside the Run dialog and set the Termination Criterion by specifying the "End Time" to 1,000 time steps. Run an FDTD analysis. At the end of the simulation, visualize the near field distributions on Sensor_1 plane.

Due to the long computation times involved in Gaussian beam simulations, reduce the fixed-cell mesh size at this point. Set the "Cell Size" to 1.2mm, 1.2mm and 0.5mm in the X, Y and Z directions, respectively. This reduces the total number of mesh cells to 887,216. Also set the FDTD Termination Criterion by specifying the "End Time" to 1,000 time steps. Run an FDTD analysis of the dielectric block with a TMz-polarized Gaussian beam and visualize the near-field distributions.

==Modeling Gaussian Beam Propagation in Left-Handed Metamaterials==

* Debye

* Drude

* Lorentz

* Left-Handed Metamaterial

From the above list, the first three types are of dielectric nature and their permittivity is characterized based on their pole types, which are first-order or second-order. A left-handed metamaterial has both permittivity and permeability tensors of uniaxial type. Each ε_rii or μ_rjj element can take one of the three Debye, Drude or Lorentz types and can have a distinct pole in general. For this project, you will set the same pole for all the six elements.

For this part of the tutorial lesson, use the project from the last part. Define a "Dispersive" material group of "Left-Handed Metamaterial" type called LEFTHANDED_1 in the Navigation Tree. To do so, right-click on the <b>Dispersive</b> item in the Navigation Tree and select <b>Insert New Left-Handed Metamaterial...</b> from the contextual menu. In the material dialog, you have to define poles for each of the six diagonal permittivity and permeability tensor elements: &epsilon;_rxx, &epsilon;_ryy, &epsilon;_rzz, &mu;_rxx, &mu;_ryy, and &mu;_rzz.

Select each permittivity or permeability component from the drop-down list labeled "Parameter" one by one. Select "Drude" from the "Pole Type" drop-down list. Keep the default value of 1 for the permittivity or permeability at infinite frequency. To define a pole, click the <b>Add Pole</b> button of the dialog and in the "Add Pole" dialog, enter 2.67e+11rad/s for "Plasma Frequency" and 1e+4rad/s for "Collision Frequency". Repeat this procedure for all the six components.

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Next, move the block object Box_1 from Dielectric_1 group to LEFTHANDED_1 group. Keep all the domain settings, Gaussian beam source, the two field sensors and the same coarser fixed-cell mesh settings from the last part.

Run an FDTD analysis of the left-handed metamaterial block with a TMz-polarized Gaussian beam and visualize the near-field distributions.

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You can easily follow the evolution of Gaussian beam field, its passage through the metamaterial slab and its exit into the lower half-space in these figures.

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{{FDTD Details}}