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fdtd:sources [2018/01/29 16:07] pklapetek |
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- | To perform a computation we need to setup at least single source of electromagnetic field. The simplest source is a point one, which is physically similar to a small dipole. More rigorous is an electric or magnetic current source which has exactly the same funcionality as the electric or magnetic dipole. | + | To perform a computation we need to setup at least single source of electromagnetic field. The simplest source is a point one, which is physically similar to a small dipole. More rigorous is an electric or magnetic current source which has exactly the same functionality as the electric or magnetic dipole. |
- | + | ||
- | If we need a plane wave to interact with our computation volume, we are no more able to use a set of point sources (unless we have extremely large computational volume which is unrealistic. Special techniques need to be used, for example one known as total/scattered field or scattered field. Both approaches are based on addition and eventually subtraction of precomputed plane wave to/from some points in the computational volume. | + | |
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// | // | ||
---- | ---- | ||
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+ | If we need a plane wave to interact with our computation volume, we are no more able to use a set of point sources (unless we have extremely large computational volume which is unrealistic. Special techniques need to be used, for example one known as total/scattered field or scattered field. Both approaches are based on addition and eventually subtraction of precomputed plane wave to/from some points in the computational volume. | ||
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+ | To get a focused source we can use plane waves summation method as published in Ref. [1]. This is based on decomposition of the ideal focused beam onto a set of plane wave with appropriate angles and phases. | ||
+ | |||
+ | ---- | ||
+ | // | ||
+ | {{ :samples:img_source_tsff.png?100|}} | ||
+ | Sample parameter file: {{samples:source_tsff.tar.gz|total/scattered focused field source}}. | ||
+ | \\ | ||
+ | A 200x200x200 computational domain with focused source and a metallic sphere made of a perfect electric conductor. | ||
+ | // | ||
+ | ---- | ||
+ | |||
+ | Layered source is a special source conditions suitable for materials with infinitely extending layers (e.g. thin films) as published in Ref. [2]. In our implementation the layers have to be laterally oriented in xy direction, so they have normal in z direction. The material can be formed by N layers in z-direction (in present implementation only dielectric and non-absorbing). Incident wave however can cross the sample at angle as well. | ||
+ | |||
+ | {{ :samples:ltsf.png?600 |}} | ||
+ | |||
+ | ---- | ||
+ | // | ||
+ | {{ :samples:img_source_ltsf.png?100|}} | ||
+ | Sample parameter file: {{samples:source_ltsf.tar.gz|layers compatible field source}}. | ||
+ | \\ | ||
+ | A 200x200x200 computational domain with source compatible with infinitely extending layers. | ||
+ | // | ||
+ | ---- | ||
+ | |||
+ | |||
+ | Layered focused source is a mixture of focused source plane wave summation and use of infinite layers in z direction, i.e. the above two sources. | ||
+ | |||
+ | ---- | ||
+ | // | ||
+ | {{ :samples:img_source_ltsff.png?100|}} | ||
+ | Sample parameter file: {{samples:source_ltsff.tar.gz|layers compatible focused field source}}. | ||
+ | \\ | ||
+ | A 200x200x200 computational domain with focused source compatible with infinitely extending layers. | ||
+ | // | ||
+ | ---- | ||
+ | |||
+ | ==== Reference ==== | ||
+ | |||
+ | [1] I.R.Capoglu, A. Taflowe, V. Backman, Optics Express 23 (2008) 19208. | ||
+ | [2] I.R. Capoglu, G.S. Smith: IEEE Transactions on Antennas and Propagation 02/2008, 56:1. | ||
+ | |||