A gradient method for design of multiorder varied-depth binary diffraction gratings

A method for the design of perfectly conducting varied-depth binary diffraction gratings is proposed. The design uses the rigorous modal expansion method and is based on the gradient search algorithm for optimization of grating structure from the condition of the generation of a desired array of diffraction orders. The designs of varied-depth binary gratings with equal order intensities are reported with an efficiency of more than 90% and root-mean square errors of 2–7%.