Multilevel diffraction gratings in the resonance domain: rigorous optimization by simulated annealing

In the design of diffractive optical elements sophisticated optimization algorithms are required that are capable of finding the optimum structure of the element, described by a set of parameters that define, e.g., the surface profile of one grating period. For binary and multilevel profiles the parameters to be optimized include the profile depth and the positions of the steps or transition points. A wide range of methods exist that are suitable for the solution of this kind of parametric optimization problems, such as direct binary search, conjugate gradient method, steepest-descent method, iterative Fourier-transformation algorithm, simulated annealing, and genetic algorithms.