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docs:become [2020/03/29 09:39] pklapetek |
docs:become [2020/04/02 11:21] pklapetek [2D calculation] |
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| The Become benchmark grating was setup with voxel spacing of 5 nm in every direction. The total computational domain size was 240x100 voxels. The grating was formed by silver, using the PLRC metal handling approach. Periodic boundary conditions were used to introduce the grating periodicity. Total/scattered field approach was used to inject the plane wave normally to the surface. TE mode calculation was used for this 2D case, which should be the p-polarisation case as requested. Near-to-far field calculation domain was set up to be outside of the plane wave source region, so only reflected and scattered electric field was propagated to the far-field. Time domain far field calculation was used. Far field data were calculated for wide range of angles for debugging purposes (i.e. not only for the directions of the particular diffraction orders). | The Become benchmark grating was setup with voxel spacing of 5 nm in every direction. The total computational domain size was 240x100 voxels. The grating was formed by silver, using the PLRC metal handling approach. Periodic boundary conditions were used to introduce the grating periodicity. Total/scattered field approach was used to inject the plane wave normally to the surface. TE mode calculation was used for this 2D case, which should be the p-polarisation case as requested. Near-to-far field calculation domain was set up to be outside of the plane wave source region, so only reflected and scattered electric field was propagated to the far-field. Time domain far field calculation was used. Far field data were calculated for wide range of angles for debugging purposes (i.e. not only for the directions of the particular diffraction orders). | ||
| - | The model setup is sketched in the following figure. | + | The model setup and a calculation snapshot of the periodic area are shown in the following figure. |
| + | The far field was evaluated from a fixed number of repetitions of the near-field values, the presented results therefore represent scattering by a finite size grating. The far field value in the direction of the maxima is however not affected by size of grating (number of repetitions), only its sharpness is affected. | ||
| + | {{:docs:model.png?600|}} | ||
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| in all the other calculations. | in all the other calculations. | ||
| - | The image below shows the normalized angular dependence of the diffraction from the grating. | + | The image below shows the normalized angular dependence of the diffraction from the (finite size) grating. |
| {{:docs:become_grating_2d_normalised.png?600|}} | {{:docs:become_grating_2d_normalised.png?600|}} | ||
| - | It can be seen that there is a slight asymmetry in the result which needs to be analyzed, probably due to wrong placement of far-field points. The average intensity of the s+1 and s-1 diffraction orders is 0.183 of the incident intensity. | + | When inspected in detail, it can be seen that there is a slight asymmetry in the result which needs to be analyzed, probably due to wrong placement of far-field points. The average intensity of the s+1 and s-1 diffraction orders is 0.178 of the incident intensity for the default silver model (not the Become one). |
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| + | List of different settings and results: | ||
| + | |||
| + | * metal setting: 6 1.03583 0 1.37537e+16 1.25733e+14 2.1735 -0.504659 7.60514e+15 4.28131e+15 0.554478 -1.48944 6.13809e+15 6.62262e+14 leads to: 0.172 * | ||
| ===== 3D calculation ===== | ===== 3D calculation ===== | ||
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| The aspects that need further investigation or tuning: | The aspects that need further investigation or tuning: | ||
| - | * polarisation correctness (TE mode is p-polarisation) | ||
| * far-field calculation postprocessing speedup, now very slow, printing many debugging data. | * far-field calculation postprocessing speedup, now very slow, printing many debugging data. | ||
| - | * cross-check metal refractive index (now relying on pre-fitted database data) | + | * cross-check metal refractive index (now relying on pre-fitted database data, which is wrong) |
| - | * correct placement of far field points (get rid of the slight asymmetry observed) | + | * there is still slight asymmetry |
| * evaluate the voxel size vs. speed vs. accuracy for the benchmark. | * evaluate the voxel size vs. speed vs. accuracy for the benchmark. | ||
docs/become.txt · Last modified: 2020/04/24 12:27 by pklapetek
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