Level set based topology optimization for optical cloaks

This letter presents a level set-based topology optimization method that provides discrete cloaking configurations with superior performance. In some cases, the amount of light scattered around the two-dimensional cloaking structures is less than one-tenth that obtained in previous studies. Optimal configurations that express different geometrical characteristics can be obtained by adjusting a regularization parameter. The obtained configurations are free from grayscales, areas of intermediate density between that of dielectric materials or air, and the use of a level set method provides clear structural boundaries. The level set functions are given on grid points and the dielectric boundaries are interpreted as lines on the iso-surface of the level set functions. The finite element method is used for light scattering analyses, computations of the adjoint variable field, and when updating the level set functions.