{"id":396865,"date":"2024-12-10T03:31:48","date_gmt":"2024-12-10T03:31:48","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/problem-about-simulating-a-diverging-metalens\/"},"modified":"2024-12-10T03:31:48","modified_gmt":"2024-12-10T03:31:48","slug":"problem-about-simulating-a-diverging-metalens","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/problem-about-simulating-a-diverging-metalens\/","title":{"rendered":"Problem about simulating a diverging metalens"},"content":{"rendered":"

<p>Hi, I'<span lang=”EN-US”>m doing the metalens simulation. I found that there is a deformation in the far-field distribution for the diverging lens, but it will not have this problem for the focusing lens. What’s the reason for this?<\/span><\/p><p><span lang=”EN-US”>Specifically, I set up a concave lens with Silicon on glass metasurface (which serves as a beam spreading function and has a negative focal length f), and then calculate the farfield at 300um using “farfieldexact3d”. I compared three methods: FDTD direct simulation \/Near field stitching\/MATLAB calculation, and found that for concave lens, the far-field results of FDTD or Near field stitching would have a shape deformation in the middle of the far-field distribution (like a dip or a ripple). The following is the scheme diagram and FDTD setup of the concave lens simulation:<\/span><\/p><p class=”MsoNormal”><span lang=”EN-US”><\/span><\/p><p class=”MsoNormal”><span lang=”EN-US”><\/span><\/p><p><span lang=”EN-US” style=”font-size: 14pt;”><span lang=”EN-US” style=”line-height: 115%; font-family: \u7b49\u7ebf;”>However, for convex lens (which have the function of focusing and the focal length f is positive), the results obtained by the three methods are very consistent, and there is no deformation. The following is the scheme diagram and FDTD setup diagram of the convex lens.<\/span><\/span><\/p><p><span lang=”EN-US” style=”font-size: 14pt;”><span lang=”EN-US” style=”line-height: 115%; font-family: \u7b49\u7ebf;”><\/span><\/span><\/p><p><span lang=”EN-US” style=”font-size: 14pt;”><span lang=”EN-US” style=”line-height: 115%; font-family: \u7b49\u7ebf;”><\/span><\/span><\/p><p class=”MsoNormal”><span lang=”EN-US”>For concave lens, I tried to raise the meshing to 3. For FDTD, the dip in the middle will change. I also tried a longer propagation distance (1000um) and found that there are still some ripples or shape deformation.<\/span><\/p><p class=”MsoNormal”><span lang=”EN-US”><\/span><\/p><\/p>\n","protected":false},"template":"","class_list":["post-396865","topic","type-topic","status-publish","hentry","topic-tag-metalens-1"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t