Simulation script to calculate absorbtion of 3D photonic nanocrystals (RCWA or FTFD)

I am working on my masters thesis, constructing and optimizing black silicon structures (conical geometrical arrays), and want to simulate the absorption of the 3D structures. I am specialized in chemical engineering so have limited experience building codes from scratch. Does anyone have a computer program for this or know where I can find one?

Thanks a lot!