{"id":292072,"date":"2023-07-07T15:13:48","date_gmt":"2023-07-07T15:13:48","guid":{"rendered":"\/forum\/forums\/topic\/spectral-variation-between-nk-import-and-gds-import-of-same-device\/"},"modified":"2023-07-07T15:13:48","modified_gmt":"2023-07-07T15:13:48","slug":"spectral-variation-between-nk-import-and-gds-import-of-same-device","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/spectral-variation-between-nk-import-and-gds-import-of-same-device\/","title":{"rendered":"Spectral variation between (n,k) import and GDS import of same device"},"content":{"rendered":"<p>Hello,<\/p>\n<p>I have recently been working with Lumopt to design a 2D (FDTD) topology-optimized wavelength demultiplexer in silicon. However, I am noticing a significant difference in the performance of two simulated devices which should have identical performance.<\/p>\n<p>The first is the output of Lumopt, as shown below. This device has been fully binarized (no index values between silicon and oxide).<\/p>\n<p><img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/07\/07-07-2023-1688742455-mceclip1.jpg\"><\/p>\n<p>This device has the transmission spectrum shown below:<\/p>\n<p><img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/07\/07-07-2023-1688742499-mceclip2.png\"><\/p>\n<p>&nbsp;<\/p>\n<p>The second device is a direct GDS trace of the first device:<img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/07\/07-07-2023-1688742527-mceclip3.jpg\"><\/p>\n<p>However, this has the transmission spectrum shown below:<\/p>\n<p><img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/07\/07-07-2023-1688742564-mceclip4.png\"><\/p>\n<p>As you can see, the spectrum is blue shifted by about 20 nm. By changing the FDTD mesh settings to use a uniform 20nm mesh (which the original device was optimized for) and aligning the mesh exactly with the device, the blue shift is reduced but still exists at about 5 nm. I have an optical index monitor on the entire device which shows no difference between the two devices. In both cases, I am using 2D FDTD simulation with PML boundaries. <\/p>\n<p>Thanks for any help you can provide.<\/p>\n","protected":false},"template":"","class_list":["post-292072","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_subscription":["288865","2592"],"_bbp_author_ip":["168.143.243.24"]," _bbp_last_reply_id":["0"]," _bbp_likes_count":["0"],"_btv_view_count":["440"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["292072"],"_bbp_forum_id":["27833"],"_bbp_engagement":["2592","288865"],"_bbp_voice_count":["2"],"_bbp_reply_count":["1"],"_bbp_last_reply_id":["292090"],"_bbp_last_active_id":["292090"],"_bbp_last_active_time":["2023-07-07 18:51:57"]},"test":"andy-li2mail-mcgill-ca"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/292072","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\/292072\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=292072"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}