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docs:become [2020/04/14 14:50] pklapetek |
docs:become [2020/04/22 14:26] pklapetek |
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| An important message is that | An important message is that | ||
| - | using the periodic approach for only a small number of repetitions does not work as it does not take into account the field on sides of the computational domain (see the technical explanation listed below for our reference). | + | using the periodic approach for only a small number of repetitions does not work as it does not take into account the field on sides of the computational domain. For large number of periodic approach repetitions we get results that are same as results from manually extending the computational domain and adding all the apertures to it. See the technical explanation listed below for our reference. |
| {{:docs:methods_explanation_humanized.png?600|}} | {{:docs:methods_explanation_humanized.png?600|}} | ||
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| however it is still unclear if this is the only effect. The backup files for this calculation are {{ :docs:2d_transmission_aperture_backup_files.tar.gz |here}}.// | however it is still unclear if this is the only effect. The backup files for this calculation are {{ :docs:2d_transmission_aperture_backup_files.tar.gz |here}}.// | ||
| + | Accuracy aspects (evaluated on the single aperture transmission): | ||
| + | * effect of time step is small, prolonging it from dt=0.5 Courant limit to 0.25 does not change the shape of the curve in a detectable way. | ||
| + | * effect of absorbing boundary type smaller or distance to the boundary much smaller (mostly invisible, below percent?). The transmission around zero order is larger slightly when Liao condition is used instead of CPML. | ||
| + | * effect of NFFF box size is up to 6 percent for the maximum difference of intensities at the first diffraction order (NFFF box sizes from 100x20 to 340x130, when y size is evaluated from the aperture plane and even for maximum NFFF the boundary in x is about 200 voxels far). Smaller NFFF box seems to be better; when it is enlarged artefacts can be seen. There is always a difference between analytical model that does not go to zero for maximum angles, and numerical model that goes to almost zero. | ||
| + | |||
| + | ---- | ||
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| + | The transition from transition geometry to reflection geometry was done first with perfect electric conductor as a grating material. Here, the validation of the periodic calculation via manual | ||
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| * default metal setting: 6 0.89583 0 13.8737e15 0.0207332e15 1.3735 -0.504659 7.59914e15 4.28431e15 0.304478 -1.48944 6.15009e15 0.659262e15 means n=(0.036 + 4.147i) and leads to first order diffraction of 0.178 | * default metal setting: 6 0.89583 0 13.8737e15 0.0207332e15 1.3735 -0.504659 7.59914e15 4.28431e15 0.304478 -1.48944 6.15009e15 0.659262e15 means n=(0.036 + 4.147i) and leads to first order diffraction of 0.178 | ||
| - | Dependence on problem size: | + | |
| + | After improving nearly everything (CPML, periodic borders, source) the result is even worse, 0.148 for the fitted metal, spacing 10 nm. However, now the result is fully symmetric and does not depend on voxel size (0.147 for spacing 5 nm). | ||
docs/become.txt · Last modified: 2020/04/24 12:27 by pklapetek
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