{"id":165614,"date":"2022-01-17T13:17:48","date_gmt":"2022-01-17T13:17:48","guid":{"rendered":"\/forum\/forums\/topic\/difference-in-results-between-fdtd-and-eme\/"},"modified":"2023-06-28T16:55:30","modified_gmt":"2023-06-28T16:55:30","slug":"difference-in-results-between-fdtd-and-eme","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/difference-in-results-between-fdtd-and-eme\/","title":{"rendered":"Difference in results between FDTD and EME"},"content":{"rendered":"<div class=\"Item-Body\">\n<div class=\"Message userContent\">\n<p>Hello,<\/p>\n<p>I am trying to design a sidewall grating with a specific coupling constant. For gratings with top etching, normally I can run a MODE solver simulation to obtain effective indexes for 2 different cross-sections of the grating and then do an analytical calculation, where a coupling constant is related to n_eff by simple formula. Then I simulate the reflectivity spectrum using transfer matrix method and I double check it with EME and FDTD solver (FDTD is possible), and they all give me quite similar results.<\/p>\n<p>With sidewall grating, however, it was not the case. I observe that my EME simulation gives a very different result from 3D FDTD, in terms that reflectivity in EME is much lower and the peak is located at different wavelength, and also there is a general significant drop of transmission. 3D FDTD simulation gives a result similar to transfer matrix calculation, but for slightly different period, but this can be attributed to different mesh settings. But I don&#039;t like to use FDTD for this structure because the simulation time is very long even for a relatively coarse mesh.<\/p>\n<div class=\"embedExternal embedImage\">\n<div class=\"embedExternal-content\">\n<a class=\"embedImage-link\" href=\"\/forum\/wp-content\/uploads\/forum-uploads\/798\/XTN46ZEAYLRK.png\" rel=\"nofollow noopener\" target=\"_blank\"><br \/>\n<img decoding=\"async\" class=\"embedImage-img\" src=\"\/forum\/wp-content\/uploads\/forum-uploads\/798\/XTN46ZEAYLRK.png\" alt=\"image.png\" \/><br \/>\n<\/a><\/p>\n","protected":false},"template":"","class_list":["post-165614","topic","type-topic","status-closed","hentry","topic-tag-eigenmode","topic-tag-fdtd"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_btv_view_count":["3346"],"_bbp_likes_count":["0"],"_bbp_subscription":["245917","267492","2592"],"_bbp_status":["publish"],"_bbp_topic_status":["unanswered"],"_bbp_topic_id":["165614"],"_bbp_forum_id":["27833"],"_bbp_engagement":["2592","245917","267492"],"_bbp_voice_count":["3"],"_bbp_reply_count":["10"],"_bbp_last_reply_id":["279889"],"_bbp_last_active_id":["279889"],"_bbp_last_active_time":["2023-04-17 21:23:30"]},"test":"a-zozuliatue-nl"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/165614","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics"}],"about":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/types\/topic"}],"version-history":[{"count":0,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/165614\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=165614"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}