Imaging of Sub-Wavelength Gratings with Different Profiles
Sub-wavelength gratings, when illuminated with paraxial light, generate only one diffraction order, and therefore no image is formed in this situation. To overcome it, non-paraxial illumination can be used. As in this example, a high-NA condenser lens is employed to provide a highly focused illumination for gratings with different profiles, and the diffracted field is to be collected by another high-NA objective. VirtualLab enables simulation of such an imaging process, including rigorous simulation of sub-wavelength gratings with Fourier modal method.