{"id":397474,"date":"2024-12-13T20:54:10","date_gmt":"2024-12-13T20:54:10","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/397474\/"},"modified":"2024-12-13T20:54:10","modified_gmt":"2024-12-13T20:54:10","slug":"397474","status":"publish","type":"reply","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/397474\/","title":{"rendered":"Reply To: Diverging simulation: gain layer under periodic metallic grating"},"content":{"rendered":"<p>&lt;p&gt;Hi Javi,&lt;\/p&gt;&lt;p&gt;I&#8217;m wondering if you&#8217;ve taken a look at the dt stability factor? Usually this is fine as the default maximum value, but we give this information about the setting:&lt;\/p&gt;&lt;p&gt;&#8221;The theoretical maximum time step is calculated from the simulation mesh size based on the Courant stability criterion. By default, Lumerical software uses a time step that is 0.99 of the theoretical maximum time step. This theoretical maximum is calculated assuming propagation of light in a homogeneous vacuum. Once physical structures and interfaces are included in the simulation, particularly when dispersive materials are involved, a smaller time step is sometimes required.&#8221;&lt;\/p&gt;&lt;p&gt;As a simpler test, you may also want to consider using a finer mesh to capture what&#8217;s happening at the boundary between the grating and gain material. We have a helpful troubleshooting guide for divergence if you haven&#8217;t already seen it: <a href=\"https:\/\/optics.ansys.com\/hc\/en-us\/articles\/11277217507603-Troubleshooting-diverging-simulations-in-FDTD\">Troubleshooting diverging simulations in FDTD &ndash; Ansys Optics<\/a>.&lt;\/p&gt;&lt;p&gt;Thanks,&lt;br&gt;Ethan&lt;\/p&gt;<\/p>\n","protected":false},"template":"","class_list":["post-397474","reply","type-reply","status-publish","hentry"],"aioseo_notices":[],"acf":[],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/replies\/397474","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/replies"}],"about":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/types\/reply"}],"version-history":[{"count":0,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/replies\/397474\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=397474"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}