{"id":292072,"date":"2023-07-07T15:13:48","date_gmt":"2023-07-07T15:13:48","guid":{"rendered":"\/forum\/forums\/topic\/spectral-variation-between-nk-import-and-gds-import-of-same-device\/"},"modified":"2023-07-07T15:13:48","modified_gmt":"2023-07-07T15:13:48","slug":"spectral-variation-between-nk-import-and-gds-import-of-same-device","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/spectral-variation-between-nk-import-and-gds-import-of-same-device\/","title":{"rendered":"Spectral variation between (n,k) import and GDS import of same device"},"content":{"rendered":"

Hello,<\/p>\n

I have recently been working with Lumopt to design a 2D (FDTD) topology-optimized wavelength demultiplexer in silicon. However, I am noticing a significant difference in the performance of two simulated devices which should have identical performance.<\/p>\n

The first is the output of Lumopt, as shown below. This device has been fully binarized (no index values between silicon and oxide).<\/p>\n

<\/p>\n

This device has the transmission spectrum shown below:<\/p>\n

<\/p>\n

 <\/p>\n

The second device is a direct GDS trace of the first device:<\/p>\n

However, this has the transmission spectrum shown below:<\/p>\n

<\/p>\n

As you can see, the spectrum is blue shifted by about 20 nm. By changing the FDTD mesh settings to use a uniform 20nm mesh (which the original device was optimized for) and aligning the mesh exactly with the device, the blue shift is reduced but still exists at about 5 nm. I have an optical index monitor on the entire device which shows no difference between the two devices. In both cases, I am using 2D FDTD simulation with PML boundaries. <\/p>\n

Thanks for any help you can provide.<\/p>\n","protected":false},"template":"","class_list":["post-292072","topic","type-topic","status-closed","hentry"],"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\n\t\t\n\t\t\n\t\t