{"id":361382,"date":"2024-04-09T17:16:10","date_gmt":"2024-04-09T17:16:10","guid":{"rendered":"\/forum\/forums\/reply\/361382\/"},"modified":"2024-04-09T17:16:10","modified_gmt":"2024-04-09T17:16:10","slug":"361382","status":"publish","type":"reply","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/361382\/","title":{"rendered":"Reply To: FDTD:: simulation of directional coupler"},"content":{"rendered":"<p>&lt;p&gt;Hi Zhongdi, please write post in Photonics forum later.&lt;\/p&gt;&lt;p&gt;This is mainly due to the fact that long and large device needs long simulation time. You can use much longer simulation time and let the autoshutoff min to terminate the simulation.&lt;\/p&gt;&lt;p&gt;Mesh 0.2um might be too coarse. Suppose the wavelength in vacuum is 1.5um, refractive index 3.4, the mini wavelength inside the material is 1.5\/3.4~0.44 um. so 0.2um is just above the Nyquist requirement. In order to get result with reasonable accuracy, it should be at least &nbsp;0.44 um\/6~0.07um, which is equivalent to mesh accuracy 1, the coarest mesh by default. Perhapes you need to upgrad your computer, as it is your tool for your projects. Please refer to the following posts:&lt;\/p&gt;&lt;p class=&#8221;MsoNormal&#8221;&gt;<a href=\"\/forum\/forums\/topic\/ansys-insight-%e5%9c%a8fdtd-%e4%bb%bf%e7%9c%9f%e7%9a%84%e8%bf%87%e7%a8%8b%e4%b8%admesh%e7%9a%84%e7%b2%be%e5%ba%a6%e5%a6%82%e4%bd%95%e8%ae%be%e7%bd%ae%ef%bc%9f\/\">Ansys Insight: &lt;span lang=&#8221;ZH-CN&#8221; style=&#8221;font-family: DengXian; mso-ascii-font-family: Calibri; mso-ascii-theme-font: minor-latin; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: Calibri; mso-hansi-theme-font: minor-latin;&#8221;&gt;\u5728&lt;\/span&gt;FDTD &lt;span lang=&#8221;ZH-CN&#8221; style=&#8221;font-family: DengXian; mso-ascii-font-family: Calibri; mso-ascii-theme-font: minor-latin; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: Calibri; mso-hansi-theme-font: minor-latin;&#8221;&gt;\u4eff\u771f\u7684\u8fc7\u7a0b\u4e2d&lt;\/span&gt;mesh&lt;span lang=&#8221;ZH-CN&#8221; style=&#8221;font-family: DengXian; mso-ascii-font-family: Calibri; mso-ascii-theme-font: minor-latin; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: Calibri; mso-hansi-theme-font: minor-latin;&#8221;&gt;\u7684\u7cbe\u5ea6\u5982\u4f55\u8bbe\u7f6e\uff1f&lt;\/span&gt; <\/a>&lt;\/p&gt;&lt;p class=&#8221;MsoNormal&#8221;&gt;<a href=\"\/forum\/forums\/topic\/ansys-insight-%e7%94%a8%e4%ba%8e%e8%ae%be%e7%bd%aemesh-accuracy%e5%af%b9%e5%ba%94%e5%a4%9a%e5%a4%a7%e7%9a%84%e7%bd%91%e6%a0%bc%e5%b0%ba%e5%af%b8\/\">Ansys Insight: &lt;span lang=&#8221;ZH-CN&#8221; style=&#8221;font-family: DengXian; mso-ascii-font-family: Calibri; mso-ascii-theme-font: minor-latin; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: Calibri; mso-hansi-theme-font: minor-latin;&#8221;&gt;\u7528\u4e8e\u8bbe\u7f6e&lt;\/span&gt;Mesh accuracy&lt;span lang=&#8221;ZH-CN&#8221; style=&#8221;font-family: DengXian; mso-ascii-font-family: Calibri; mso-ascii-theme-font: minor-latin; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: Calibri; mso-hansi-theme-font: minor-latin;&#8221;&gt;\u5bf9\u5e94\u591a\u5927\u7684\u7f51\u683c\u5c3a\u5bf8&lt;\/span&gt; <\/a>&lt;\/p&gt;&lt;p&gt;As for diverging, it depends on the mesh size. You can use thicker PML along propagation direction. To reduce memory requirement, you could use Metal BCs in y and z. Make sure the source mode is correct.&nbsp;&lt;\/p&gt;&lt;p class=&#8221;MsoNormal&#8221;&gt;<a href=\"\/forum\/forums\/topic\/ansys-insight-fdtd-he-varfdtd-changjiandefasanyuanyinyijichuli\/\">Ansys Insight: FDTD &lt;span lang=&#8221;ZH-CN&#8221; style=&#8221;font-family: DengXian; mso-ascii-font-family: Calibri; mso-ascii-theme-font: minor-latin; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: Calibri; mso-hansi-theme-font: minor-latin;&#8221;&gt;\u548c&lt;\/span&gt; varFDTD &lt;span lang=&#8221;ZH-CN&#8221; style=&#8221;font-family: DengXian; mso-ascii-font-family: Calibri; mso-ascii-theme-font: minor-latin; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: Calibri; mso-hansi-theme-font: minor-latin;&#8221;&gt;\u5e38\u89c1\u7684\u53d1\u6563\u539f\u56e0\u4ee5\u53ca\u5904\u7406&lt;\/span&gt; <\/a>&lt;span style=&#8221;mso-spacerun: yes;&#8221;&gt;&nbsp;&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&nbsp;&lt;\/p&gt;<\/p>\n","protected":false},"template":"","class_list":["post-361382","reply","type-reply","status-publish","hentry"],"aioseo_notices":[],"aioseo_head":"\n\t\t<!-- All in One SEO 4.9.10 - aioseo.com -->\n\t<meta name=\"description\" content=\"Hi Zhongdi, please write post in Photonics forum later.This is mainly due to the fact that long and large device needs long simulation time. You can use much longer simulation time and let the autoshutoff min to terminate the simulation.Mesh 0.2um might be too coarse. Suppose the wavelength in vacuum is 1.5um, refractive index 3.4,\" \/>\n\t<meta name=\"robots\" content=\"max-image-preview:large\" \/>\n\t<link rel=\"canonical\" href=\"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/361382\/\" \/>\n\t<meta name=\"generator\" content=\"All in One SEO (AIOSEO) 4.9.10\" \/>\n\t\t<meta property=\"og:locale\" content=\"en_US\" \/>\n\t\t<meta property=\"og:site_name\" content=\"Ansys Learning Forum | Ansys Innovation Space\" \/>\n\t\t<meta property=\"og:type\" content=\"article\" \/>\n\t\t<meta property=\"og:title\" content=\"Reply To: FDTD:: simulation of directional coupler | Ansys Learning Forum\" \/>\n\t\t<meta property=\"og:description\" content=\"Hi Zhongdi, please write post in Photonics forum later.This is mainly due to the fact that long and large device needs long simulation time. 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