{"id":439313,"date":"2025-08-14T15:22:05","date_gmt":"2025-08-14T15:22:05","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/lumopt-grating-coupler-optimization-limits\/"},"modified":"2025-08-14T15:22:05","modified_gmt":"2025-08-14T15:22:05","slug":"lumopt-grating-coupler-optimization-limits","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/lumopt-grating-coupler-optimization-limits\/","title":{"rendered":"lumopt grating coupler optimization limits"},"content":{"rendered":"<p>&lt;p&gt;Hi!&lt;\/p&gt;&lt;p&gt;Im currently using lumopt to design a grating coupler in 2D FDTD with a different materials and geometry compared to the provided example. I fistly did a primitive parameter sweep for x0 and R to reach a coupling efficiency of approximately 30%, and expect to improve it with lumopt optimization. However, the optimization process seems to increase the FoM and approaching the FoM with initial parameter sweep (30%) and the maximum FoM is even bit less, instead of exceeding it.&lt;\/p&gt;&lt;p&gt;Also, the examples provided by lumerical website seems similar to this, the optimization of FoM approaches the initial parameter value instead of higher. It seems not &#8216;optimizing the grating coupler&#8217;, but making the gratings more random but not improving the performance. May I know it&#8217;s because of my seetings or it&#8217;s just how the algorithm works?&lt;\/p&gt;&lt;p&gt;Best, Qiyuan&lt;\/p&gt;&lt;p&gt;<img decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2025\/08\/14-08-2025-1755184718-mceclip0.png\" \/>&lt;\/p&gt;<\/p>\n","protected":false},"template":"","class_list":["post-439313","topic","type-topic","status-publish","hentry","topic-tag-gratingcoupler-1","topic-tag-inverse-design-of-grating-coupler-2","topic-tag-lumopt-1"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_forum_id":["27833"],"_bbp_topic_id":["439313"],"_bbp_author_ip":["131.155.236.16"],"_bbp_last_reply_id":["439896"],"_bbp_last_active_id":["439896"],"_bbp_last_active_time":["2025-08-21 18:43:15"],"_bbp_reply_count":["4"],"_bbp_reply_count_hidden":["0"],"_bbp_voice_count":["2"],"_bbp_engagement":["542126","443894"],"_btv_view_count":["489"],"_bbp_topic_status":["unanswered"],"_bbp_notification_enabled":["542126","473055"],"_edit_lock":["1755189526:473055"],"_bbp_subscription":["443894","542126"]},"test":"q-shengtue-nl"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/439313","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\/439313\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=439313"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}