{"id":167741,"date":"2022-03-25T12:25:55","date_gmt":"2022-03-25T12:25:55","guid":{"rendered":"\/forum\/forums\/topic\/a-question-regarding-pml-related-divergence-in-fdtd-simulations-of-a-silicon-waveguide\/"},"modified":"2022-03-29T07:26:41","modified_gmt":"2022-03-29T07:26:41","slug":"a-question-regarding-pml-related-divergence-in-fdtd-simulations-of-a-silicon-waveguide","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/a-question-regarding-pml-related-divergence-in-fdtd-simulations-of-a-silicon-waveguide\/","title":{"rendered":"A question regarding PML related divergence in FDTD simulations of a silicon waveguide."},"content":{"rendered":"
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Hi all!<\/p>\n

I am having some problems when simulating (FDTD) a silicon waveguide turn with some subwavelength structures at the side. I am using two ports. One for mode excitation and another to monitor the output. I am using a PML BC. All structures are extended through the PML region. The simulation appears to be running fine and the autoshutoff level drops down to around 1e-4, however it never reaches 1e-5 and at some point starts to rise unlimitedly. When observing the movie monitor, simulation appears physicaly correct and the light appears to be propagating as expected. Long after most of the light appears to be absorbed by the PML, the field around the input port starts to rise unlimitedly causing the simulation to diverge. I tried to change the PML profile to stable and in that case the simulation converges and the autoshutoff level of 1e-5 is reached. However in this case there apears to be a significant back reflection from the PML back into the waveguide that is rendering simulation results nonphysical. This reflection can also be seen on the movie monitor. The simulations take a significant amount of time and I am somewhat time limited. Since I am trying to avoid extensive convergence testing, I decided to ask here first whether anyone would have an insight into my problem. My question is what do you think I should change first to achieve a stable simulation? Any help would be gratly appreciated. <\/p>\n

Andraz<\/p>\n","protected":false},"template":"","class_list":["post-167741","topic","type-topic","status-closed","hentry","topic-tag-convergence","topic-tag-dielectric-waveguide","topic-tag-fdtd","topic-tag-lumerical","topic-tag-pml"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t