Dear Devika,
My very first attempt is using FDE, but I realized that FDE only takes into accounts of the material's imaginary refractive index (I ran two different simulations, one with actual material parameters with , one with object-defined material parameters without imagnary refractive index). It turns out that the one without imagnary refractive index gave no propagation loss. This is why I used VarFDTD (as the authors mentioned). I will check out more carefully the link you sent me.
Thank you
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