Drude Material Optical Scatterer - CST2013 MWS Examples

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General Description

This example calculates the "Extinction Cross Section" of a metal coated silica sphere at optical frequencies.

Structure Generation

First, general settings concerning the background material, the absorbing boundary condition (open add space) and the units (nm) are defined. The actual structure is created drawing two spheres and using a Boolean insert. The silica material is defined as simple "normal" material with an epsilon value of 2.08. The metal material properties are modelled by using "Drude dispersion model". The corresponding Drude parameters can be extracted by using the macro Home: Macros Materials Create Drude Parameters for Optical Applications.

Solver Setup

For accurate simulations, it is required to refine the mesh for the Drude material. In this model a mesh resolution of 1 nm is used by selecting the metal sphere and using local mesh properties. A plane wave is used to excite the structure. Because of the resonant behavior at certain frequencies (plasmon generation) an accuracy setting of -50 dB is used.

Post Processing

The broadband scattering response is extracted by using a broadband farfield monitor. This monitor already automatically writes the total radar cross section (Total RCS) as well as the total absorption cross section (Total ACS) into the 1D Results folder. The sum of these values is derived as the extinction cross section by usage of a "Mix 1D" result template. For optical applications, it is common to plot any result against the wavelength, so again a "Mix 1D" result template is used to change the X axes from frequency to wavelength: