{"id":359412,"date":"2024-03-28T10:40:33","date_gmt":"2024-03-28T10:40:33","guid":{"rendered":"\/forum\/forums\/topic\/bandstructure-disagreement-fdtd-vs-mpb\/"},"modified":"2024-03-28T10:40:33","modified_gmt":"2024-03-28T10:40:33","slug":"bandstructure-disagreement-fdtd-vs-mpb","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/bandstructure-disagreement-fdtd-vs-mpb\/","title":{"rendered":"Bandstructure disagreement, FDTD vs MPB"},"content":{"rendered":"<div>I have noticed a strong disagreement in bandstructure calculation in comparison to MIT photonic bands.&nbsp;<\/div>\n<div>&nbsp;<\/div>\n<div>To demonstrate this, here is the bandstructure obtained from the band structure example: https:\/\/optics.ansys.com\/hc\/en-us\/articles\/360041566614-Rectangular-Photonic-Crystal-Bandstructure<\/div>\n<div>Square lattice 2D TM mode:<\/div>\n<p><img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2024\/03\/28-03-2024-1711621138-mceclip0.png\"><\/p>\n<p>Calculating a bandstructure of exactly the same structure using MPB (https:\/\/mpb.readthedocs.io\/en\/latest\/) I obtain:<img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2024\/03\/28-03-2024-1711621139-mceclip2.png\"><\/p>\n<div>Those band structures are more or less in agreement, the shape is identical, and the energy axis seems to be a little scaled (apparent at 0.4 energy scale)<\/div>\n<div>&nbsp;<\/div>\n<div>Now, increasing the refractive index in both solvers to 10 leads to the following results:<\/div>\n<p><img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2024\/03\/28-03-2024-1711621759-mceclip4.png\"><\/p>\n<p><img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2024\/03\/28-03-2024-1711621786-mceclip5.png\"><\/p>\n<div>The shape of the bands is similar again, but this time, the energy axis is drastically scaled. Other calculation methods hint towards MPB being correct.<\/div>\n<div>How do I combat this issue of energetical disagreement for high permittivity simulations?<\/div>\n<div>&nbsp;<\/div>\n<div>Thank you,<\/div>\n<div>Martin<\/div>\n<p><\/p>\n","protected":false},"template":"","class_list":["post-359412","topic","type-topic","status-closed","hentry","topic-tag-Photoniccrystal-1","topic-tag-bandstructure-1","topic-tag-fdtd"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_subscription":["5970","2592"],"_bbp_author_ip":["23.206.193.59"]," _bbp_last_reply_id":["0"]," _bbp_likes_count":["0"],"_btv_view_count":["842"],"_bbp_topic_status":["unanswered"],"_bbp_topic_id":["359412"],"_bbp_forum_id":["27833"],"_bbp_engagement":["2592","5970"],"_bbp_voice_count":["2"],"_bbp_reply_count":["3"],"_bbp_last_reply_id":["360332"],"_bbp_last_active_id":["360332"],"_bbp_last_active_time":["2024-04-03 16:02:59"]},"test":"veiskarlov-mff-cuni-cz"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/359412","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\/359412\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=359412"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}