LumOpt Geometries - FunctionDefinedPolygon Question

tgartnertgartner Member Posts: 5


I am trying to use the example of Inverse Design of Grating Coupler (2D) ( and had a question about the functionality of the FunctionDefinedPolygon script used in the model (

As I understand it, the FunctionDefinedPolygon script creates the geometry of the gratings in question with the inputs. It defines eps_out and eps_in as the permittivity of the material around the polygon (which here would be the grating grooves) and the polygon itself (the grating teeth), respectively.

My question is, for a three layer waveguide/grating, where the waveguide/grating (middle layer) is silicon, the substrate (bottom layer) is SiO2, and the top cladding is air (top layer, so this would be the top cladding and the grating grooves), does this function work if the gratings are fully etched? (eg. the permittivity of the material around the polygon (grating tooth) is air on the top and sides, but SiO2 underneath? Or when it draws the polygon will it incorrectly assign the material underneath the polygon as air if I define eps_out = 1**2 and eps_in = 3.42**2? For reference here is the script from the example files that calls the function:



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