{"id":166348,"date":"2022-02-13T06:33:02","date_gmt":"2022-02-13T06:33:02","guid":{"rendered":"\/forum\/forums\/topic\/difference-in-results-between-fdtd-and-mode-fde-for-waveguide\/"},"modified":"2022-02-15T16:13:23","modified_gmt":"2022-02-15T16:13:23","slug":"difference-in-results-between-fdtd-and-mode-fde-for-waveguide","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/difference-in-results-between-fdtd-and-mode-fde-for-waveguide\/","title":{"rendered":"Difference in results between FDTD and MODE (FDE) for waveguide?"},"content":{"rendered":"<div class=\"Item-Body\">\n<div class=\"Message userContent\">\n<p>I created a simple straight Si waveguide surrounded by SiO2 in both FDTD and MODE. I would like to find the mode at the tip of the waveguide (and later compute the overlap between the waveguide mode and a fibre mode).<\/p>\n<p>In FDTD, I added a mode source (forward direction) at the left edge of the waveguide and a monitor at the right edge to obtain the field profile. <\/p>\n<p>Separately In MODE, I added an FDE solver (2-dimensional) at the right edge of the waveguide, at the same place where I had the FDTD monitor in the other simulation. <\/p>\n<p>I expected both of these methods to produce the same output mode since they correspond to the same structure. I ensured that both solvers extend beyond the boundaries of the structure. However, FDTD and FDE do not produce the same mode, because when I calculate the overlap between the mode from FDTD and the mode from FDE, the overlap is &lt; 0.5 when it should be close to 1. They also give very different optimized overlaps with a fiber mode. (Because we are interested in the overlap\/power coupling and not the absolute power, we are not normalizing the modes, which should be ok, I think.)<\/p>\n<p>How can I ensure that FDTD and FDE will give the same result? I am using the exact same waveguide and oxide geometry for both. Because this is a straight waveguide, the length of the waveguide should not matter, right? The mode profile at the tip should be the same regardless of the waveguide length. Thank you.<\/p>\n","protected":false},"template":"","class_list":["post-166348","topic","type-topic","status-closed","hentry","topic-tag-LumericalFDTD-1","topic-tag-LumericalMode-1","topic-tag-waveguide-1"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_btv_view_count":["2190"],"_bbp_likes_count":["0"],"_bbp_subscription":["246685"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["166348"],"_bbp_forum_id":["27833"],"_bbp_engagement":["2592","246685"],"_bbp_voice_count":["2"],"_bbp_reply_count":["3"],"_bbp_last_reply_id":["205325"],"_bbp_last_active_id":["205325"],"_bbp_last_active_time":["2022-02-15 16:13:23"]},"test":"aberg05mit-edu"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/166348","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\/166348\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=166348"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}