Solution box: SOLBOX-06

The topic of this issue is an optimization problem (SOLBOX-06), involving nanocubes at optical frequencies. This type of array arrangement (namely, a nanoarray) is useful for controlling and directing optical waves in numerous applications, such as optical links, sensing, and energy harvesting [1–6]. A particular aim in SOLBOX-06 is to maximize the scattering or radiation of a given array structure in desired directions. Despite the number of unknowns being relatively small, the main challenge is the size of the optimization space, which is grows exponentially with the number of nanocubes. In addition, the nanocubes are made of silver (Ag). They must therefore be modeled as penetrable objects with negative real permittivity, at optical frequencies. The sample solutions also included in this issue use genetic algorithms, combined with a solver based on surface integral equations, and the Multilevel Fast Multipole algorithm. Alternative solutions of the same problems with other solvers, possibly using different and more-efficient optimization tools (heuristic or gradient-based) and solution methods (e.g., volume integral equations, other types of acceleration algorithms, iterative solvers, and discretization techniques), are welcome. Please submit your solutions to ozergul@metu.edu.tr.