Reply To: Lumopt: Unable to calculate gradient after changing dielectric constant

[anna.wirth-singh]

Hi Fachien,

Thank you for providing information about your case. Could you please clarify, is this a topology optimization or a shape outline optimization? 

If you are not already doing so, please try adding a mesh override region over the optimizable geometry. Lumerical uses an adaptive mesh, so in inverse design the mesh will update as the geometry is changed. This can sometimes cause issues calculating the gradients in lumopt. So the solution is to use a mesh override region over the optimizable geometry to ensure that the mesh grid remains fixed during optimization. 

Also, I have one follow-up question. After you change the dielectric constants, does the starting simulation produce the expected results? It would be good to double check that there is no issue with the initial simulation. 

Best,

Anna