Rigorous microlens design using vector electromagnetic method combined with simulated annealing optimization.

In this paper, finite-aperture diffractive optical element with its critical dimension smaller than illumination wavelength is modeled and optimized using an integrated method. This method employs rigorous analysis model based on Finite Difference Time Domain (FDTD), and simulated annealing (SA) global search algorithm. Numerical results reveal that the diffraction efficiency of the 8-step microlens quickly climbs to its global optimum along with the optimization process, which manifests its global search ability. The design algorithm and implementation are discussed in details. Considering its time consuming efficiency and global search ability, our method provides valuable reference value in practical multistep microlens design.