Hello Aveneesh,
The answer to your question will depend on what version of the OptiFDTD product you are using. Current versions of the product provide a robust means for defining materials based on their dispersive properties. The fitting to Lorentz-Drude materials can also be done by loading in the refractive index versus wavelength. This method will provide support for all of the materials defined within your paper.
The absorption versus wavelength can be done by using the VB Script to calculate the power spectra of observation areas before and after the region of interest and calculating the difference.
Scott
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