{"id":163373,"date":"2021-10-25T19:02:45","date_gmt":"2021-10-25T19:02:45","guid":{"rendered":"\/forum\/forums\/topic\/question-on-s-matrix-and-mode-overlap-in-fde\/"},"modified":"2022-01-05T19:26:53","modified_gmt":"2022-01-05T19:26:53","slug":"question-on-s-matrix-and-mode-overlap-in-fde","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/question-on-s-matrix-and-mode-overlap-in-fde\/","title":{"rendered":"Question on S matrix and mode overlap in FDE"},"content":{"rendered":"<div class=\"Item-Body\">\n<div class=\"Message userContent\">\n<p>Hi All<\/p>\n<p>I&#039;m designing a Fiber-chip coupler and find a wired thing. <\/p>\n<p>From this example, <a href=\"https:\/\/support.lumerical.com\/hc\/en-us\/articles\/360042305354-Edge-coupler\" rel=\"nofollow\">https:\/\/support.lumerical.com\/hc\/en-us\/articles\/360042305354-Edge-coupler<\/a><\/p>\n<p>The definition of total coupling efficiency is mode overlap between fiber mode and the coupler mode times the adiabatic mode transfer efficiency from coupler tip mode to the waveguide mode. <\/p>\n<p>In the example project, there is no problem, the mode over lap is about 90%(or higher) and the total coupling efficiency is about 85%. So we can know that the adiabatic transfer efficiency is also higher than 90%. <\/p>\n<p>When I make some change on the structure, something wired happened. For example, deleting the three silicon nitride layers. The mode overlap will drop greatly, to about 50% (without fiber position optimization). However, the transmission efficiency (S21^2) is 70%. This is wired because follow the principle of coupler, the 70% should come from 50% times the adiabatic transfer efficiency. Even if the second efficiency is 100%, the result should not be 70%. <\/p>\n<p>Do someone know where this problem comes from? I&#039;m really confused&#8230;..<span class=\"safeEmoji nativeEmoji\">?<\/span><\/p>\n","protected":false},"template":"","class_list":["post-163373","topic","type-topic","status-closed","hentry","topic-tag-adiabatic","topic-tag-coupler-1","topic-tag-fiber"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_author_ip":[""],"_bbp_old_reply_author_name_id":["Anonymous"],"_bbp_old_is_reply_anonymous_id":["false"],"_btv_view_count":["369"],"_bbp_likes_count":["0"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["163373"],"_bbp_forum_id":["27833"],"_bbp_engagement":["2592","215234"],"_bbp_voice_count":["2"],"_bbp_reply_count":["3"],"_bbp_last_reply_id":["195724"],"_bbp_last_active_id":["195724"],"_bbp_last_active_time":["2022-01-05 19:26:53"]},"test":"iqnloquantumlah-org"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/163373","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\/163373\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=163373"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}