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fdtd:sources [2018/01/29 16:06] pklapetek |
fdtd:sources [2018/08/28 15:17] 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. | + | |
| ---- | ---- | ||
| Line 12: | Line 9: | ||
| {{ :samples:img_source_point.png?100|}} | {{ :samples:img_source_point.png?100|}} | ||
| Sample parameter file: {{samples:source_point.tar.gz|point source}}. | Sample parameter file: {{samples:source_point.tar.gz|point source}}. | ||
| + | \\ | ||
| A 200x200x200 computational domain with single point source and a metallic sphere made of a perfect electric conductor. | A 200x200x200 computational domain with single point source and a metallic sphere made of a perfect electric conductor. | ||
| // | // | ||
| ---- | ---- | ||
| + | |||
| + | 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. | ||
| + | |||
| Line 23: | Line 24: | ||
| {{ :samples:img_source_tsf.png?100|}} | {{ :samples:img_source_tsf.png?100|}} | ||
| Sample parameter file: {{samples:source_tsf.tar.gz|total/scattered field source}}. | Sample parameter file: {{samples:source_tsf.tar.gz|total/scattered field source}}. | ||
| + | \\ | ||
| A 200x200x200 computational domain with total/scattered field source and a metallic sphere made of a perfect electric conductor. | A 200x200x200 computational domain with total/scattered field source and a metallic sphere made of a perfect electric conductor. | ||
| // | // | ||
| Line 33: | Line 35: | ||
| // | // | ||
| {{ :samples:img_source_sf.png?100|}} | {{ :samples:img_source_sf.png?100|}} | ||
| - | Sample parameter file: {{samples:source_sf.tar.gz|point source}}. | + | Sample parameter file: {{samples:source_sf.tar.gz|scattered field source}}. |
| + | \\ | ||
| A 200x200x200 computational domain with scattered field source and a metallic sphere made of a perfect electric conductor. | A 200x200x200 computational domain with scattered field source and a metallic sphere made of a perfect electric conductor. | ||
| // | // | ||
| ---- | ---- | ||
| + | |||
| + | 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. | ||
| + | // | ||
| + | ---- | ||
| + | |||
| + | Finally, some of the sources can be also altered after they are set, e.g. to change the source profile. | ||
| + | This is the case of LTSF and TSF (in z direction) where we can multiply the plane wave entering the computational domain by a Gaussian to get a slightly diverging Gaussian beam. | ||
| + | |||
| + | ---- | ||
| + | // | ||
| + | {{ :samples:img_source_gaussian.png?100|}} | ||
| + | Sample parameter file: {{samples:source_gaussian.tar.gz|TSF Gaussian source}}. | ||
| + | \\ | ||
| + | A 200x200x200 computational domain with total/scattered field source, incidient at angle and multiplied by a Gaussian function. | ||
| + | // | ||
| + | ---- | ||
| + | |||
| + | |||
| + | ==== 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. | ||
| + | |||
fdtd/sources.txt · Last modified: 2018/08/28 15:18 by pklapetek
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