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Bragg_Diffraction.gif (480 × 480 pixels, file size: 13.34 MB, MIME type: image/gif, looped, 120 frames, 12 s)

Summary

Description
English: A line of point scatterers behave approximately as a partial mirror. When the scatterers are arranged in a crystal, each line will reflect light, and all of those reflections will interfere with each other. (Animation made for scalar fields in 2D)
Date
Source https://twitter.com/j_bertolotti/status/1261314633673080835
Author Jacopo Bertolotti
Permission
(Reusing this file)
https://twitter.com/j_bertolotti/status/1030470604418428929

Mathematica 12.0 code

sinstep[t_] := Sin[\[Pi]/2 t]^2
stopstep[t_] := t (2 - t);
\[Lambda] = Sqrt[2];
k0 = (2 \[Pi])/\[Lambda];
c = 1;
\[Omega] = c k0;
\[Alpha] = 4/(k0^2 I);
\[Sigma] = (k0^3 Norm[\[Alpha]]^2)/4;
G[r_] := N[I/4 HankelH1[0, k0 Norm[r] ]];
ReMapC[x_] := RGBColor[(Cos[2 \[Pi] x] + 1)/2 UnitStep[x - 0.5], 0, (Cos[2 \[Pi] x] + 1)/2 UnitStep[0.5 - x]];
\[Theta] = -\[Pi]/4;
E0[x_, y_] := E^(I k0 (Cos[\[Theta]] x + Sin[\[Theta]] y))/4 E^(-((-Sin[\[Theta]] x + Cos[\[Theta]] y)^2/(2 3^2)));

p0 = Table[
   sources = {stopstep[t] ({-5, 0} - {11, 0}) + {11, 0}};
   nsources = Dimensions[sources][[1]];
   DensityPlot[
    Re[E0[x, y]/4 + Sum[G[{x, y} - sources[[j]]] E0[sources[[j, 1]], sources[[j, 2]] ], {j, 1, nsources}] ], {x, -10, 10}, {y, -10, 10}, PlotPoints -> 100, ColorFunction -> ReMapC, Frame -> False, PlotRange -> {-0.5, 0.5}, RegionFunction -> Function[{x, y}, And @@ Table[Norm[{x, y} - sources[[j]]] > 0.2, {j, 1, nsources}]  ], Epilog -> { Black, Thick, Table[Circle[sources[[j]], 0.2], {j, 1, nsources}]}]
   , {t, 0, 1, 0.05}];

p1 = Table[
   sources = Table[{j, 0}, {j, -5, k, 1}];
   nsources = Dimensions[sources][[1]];
   DensityPlot[
    Re[E0[x, y]/10 + Sum[G[{x, y} - sources[[j]]] E0[sources[[j, 1]], sources[[j, 2]] ], {j, 1, nsources}] ], {x, -10, 10}, {y, -10, 10}, PlotPoints -> 100, ColorFunction -> ReMapC, Frame -> False, PlotRange -> {-0.5, 0.5}, RegionFunction -> Function[{x, y}, And @@ Table[Norm[{x, y} - sources[[j]]] > 0.2, {j, 1, nsources}]  ], Epilog -> {White, Table[Disk[sources[[j]], 0.2], {j, 1, nsources}], Black, Thick, 
      Table[Circle[sources[[j]], 0.2], {j, 1, nsources}]}]
   , {k, -4, 5, 1}];

p2 = Table[
   sources = 
    sinstep[t]*(Table[{j, j - 5}, {j, -5, 5, 1}] - Table[{j, 0}, {j, -5, 5, 1}]) + Table[{j, 0}, {j, -5, 5, 1}];
   nsources = Dimensions[sources][[1]];
   DensityPlot[
    Re[E0[x, y]/10 + Sum[G[{x, y} - sources[[j]]] E0[sources[[j, 1]], sources[[j, 2]] ], {j, 1, nsources}] ], {x, -10, 10}, {y, -10, 10}, PlotPoints -> 100, ColorFunction -> ReMapC, Frame -> False, PlotRange -> {-0.5, 0.5}, RegionFunction -> Function[{x, y}, And @@ Table[ Norm[{x, y} - sources[[j]]] > 0.2, {j, 1, nsources}]  ], Epilog -> {White, Table[Disk[sources[[j]], 0.2], {j, 1, nsources}], Black, Thick, 
      Table[Circle[sources[[j]], 0.2], {j, 1, nsources}]}]
   , {t, 0, 1, 0.051}];

p3 = Table[
   sources = Flatten[Table[{x, y} , {x, -5, 5, 1}, {y, 0, -k, -1}], 1];
   nsources = Dimensions[sources][[1]];
   DensityPlot[
    Re[E0[x, y]/10 + Sum[G[{x, y} - sources[[j]]] E0[sources[[j, 1]], sources[[j, 2]] ], {j, 1, nsources}] ], {x, -10, 10}, {y, -10, 10}, PlotPoints -> 100, ColorFunction -> ReMapC, Frame -> False, PlotRange -> {-0.5, 0.5}, RegionFunction -> Function[{x, y}, And @@ Table[Norm[{x, y} - sources[[j]]] > 0.2, {j, 1, nsources}]  ], Epilog -> {White, Table[Disk[sources[[j]], 0.2], {j, 1, nsources}], Black, Thick, 
      Table[Circle[sources[[j]], 0.2], {j, 1, nsources}]}]
   , {k, 0, 3, 1}];

ListAnimate[Join[p0, p1, p2, Reverse[p2], p3, Table[p3[[-1]], {10}] , Reverse[p3], Reverse[p1], Reverse[p0] ] ]

Licensing

I, the copyright holder of this work, hereby publish it under the following license:
Creative Commons CC-Zero This file is made available under the Creative Commons CC0 1.0 Universal Public Domain Dedication.
The person who associated a work with this deed has dedicated the work to the public domain by waiving all of their rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law. You can copy, modify, distribute and perform the work, even for commercial purposes, all without asking permission.

Captions

Visualization of Bragg diffraction

Items portrayed in this file

depicts

15 May 2020

image/gif

03116ede2036c6bc9df2609544b4a179a44b68ee

13,990,054 byte

11.999999999999973 second

480 pixel

480 pixel

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Date/TimeThumbnailDimensionsUserComment
current11:37, 16 May 2020Thumbnail for version as of 11:37, 16 May 2020480 × 480 (13.34 MB)BertoUploaded own work with UploadWizard

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