{"id":382551,"date":"2024-09-12T22:07:02","date_gmt":"2024-09-12T22:07:02","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/far-field-projection-of-gaussian-beam\/"},"modified":"2024-09-12T22:07:02","modified_gmt":"2024-09-12T22:07:02","slug":"far-field-projection-of-gaussian-beam","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/far-field-projection-of-gaussian-beam\/","title":{"rendered":"far field projection of gaussian beam"},"content":{"rendered":"<p>&lt;p&gt;I&#8217;m trying to understand the far field projection of a gaussian source with NA=0.1. I calculated the far field projection from fields measured on a 2d monitor that is normal to the propagation direction. With the &#8216;thin lens&#8217; option, there is a hole at the center of the beam. Is this expected\/correct? if so, why? Given that my wavelength~1 um and beam waist ~3 um, I thought I should use &#8216;thin lens&#8217;. I also tried applying the &#8216;scalar approximation&#8217;. The resulting beam cross section is qualitatively different, and more like what I expected. Does it mean I should use salar approx for this beam? Previously I also did some scattering\/force calculations using the E- and H-fields from monitors; those results are at lease qualitatively similar regardless of how I configured the gaussian source.&lt;\/p&gt;&lt;p&gt;<img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2024\/09\/12-09-2024-1726177425-incident_NA01_beamprofile.png\" alt=\"\" width=\"758\" height=\"615\" \/>&lt;\/p&gt;&lt;p&gt;<img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2024\/09\/12-09-2024-1726177444-incident_NA01_beamprofile-scalarApp.png\" alt=\"\" width=\"770\" height=\"626\" \/>&lt;\/p&gt;<\/p>\n","protected":false},"template":"","class_list":["post-382551","topic","type-topic","status-publish","hentry","topic-tag-gaussianbeam-1","topic-tag-fdtd"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_subscription":["77315","2592"],"_bbp_author_ip":["171.66.12.55"],"_btv_view_count":["201"],"_bbp_topic_status":["unanswered"],"_bbp_topic_id":["382551"],"_bbp_forum_id":["27833"],"_bbp_engagement":["2592","77315"],"_bbp_voice_count":["2"],"_bbp_reply_count":["3"],"_bbp_last_reply_id":["383244"],"_bbp_last_active_id":["383244"],"_bbp_last_active_time":["2024-09-19 23:28:39"]},"test":"yuqizhustanford-edu"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/382551","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\/382551\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=382551"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}