Learning Forum

[Kessem Zamir]

Dear Sir/ Madam,

I'm currently working on a periodic structure consisting of two waveguides with grating, in FDTD using Bloch boundary condition.

I want to do an optimization on the waveguides' and gratings' parameters in order to get some feature in the dispersion relation.

I would like that my cost function will be a function of the eigenvectors of the transfer matrix of a unit cell of the structure (which depends on the waveguides parameters). I wasn't able to find how to do a simulation with optimization that its cost function is related to the eigenvector. Is there a feasible approach to accomplish this task?

I appreciate your help,

Kessem

[Guilin Sun]

FOM (Figure of Merit) can only be a scalar, one value from the built-in particle swam optimization. eigen vector is a not  a scale factor. So you will need to manuliplate the eigenvector to form a FOM.

For more than one FOM value, other third tools may have multi-targets algorithms that you might use. Currently Lumerical can use Matlab and Python. You may explore them.

 

[Kessem Zamir]

Dear Guilin,

Thank you for your answer. Indeed I intend to manuliplate the eigenvector so my cost function (FOM) will be a scalar, sorry if it wasn't clear.

I am encountering difficulties in translating this concept into code. Specifically, I am unsure about the implementation details regarding the extraction of eigenvectors and subsequent optimization within the FDTD framework.

Could you possibly provide me with an example or point me towards a similar simulation that demonstrates the manipulation of eigenvectors and subsequent optimization? Any guidance or resources would be greatly appreciated.

Thank you for your assistance.

 

[Guilin Sun]

I guess you know how to get the eigen vector: https://optics.ansys.com/hc/en-us/articles/360034925793-eig-Script-command

You will need to get the eigen vector in an analysis group; in "model"; or in Custom FOM if possible: 

https://optics.ansys.com/hc/en-us/articles/360034922953-Optimization-utility

examples:

Inverse design of y-branch

Inverse design of waveguide crossing