The two solutions are different. In OptiFDTD you will design the lens and extract the reflectivity information. You will need to set the proper materials and geometry to attain your goals of reflectivity. In OptiSystem, you set the reflectivity and use the component in a larger system. To observe the wavelength dependent reflectivity you would need to use the Matlab component or you might be able to mimic the lens with a Fiber Bragg Grating.
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