Grating Calculator is a freeware application for the Calculation of Focal Planes of General Diffraction Gratings, from Rowland Type to the most modern aperiodic line density concave gratings used for soft x-ray diffraction.
MRCWA - Multilayer Rigorous Coupled Wave Analysis is a fast, flexible optical grating solver. It calculates an exact solution to the Maxwell equations for the diffraction of light from an optical grating with arbitrary profile and materials.