“…Topology optimization is currently regarded to be the most robust methodology for the inverse determination of material distribution in structures that meet given structural performance criteria. It was first developed for elastic material response by Bendsøe & Kikuchi [35], and then was extended to a variety of application areas, including acoustic, electromagnetic, fluidic and thermal problems [16,[20][21][22][24][25][26][27][28][29][30][31][32][33][36][37][38][39][40][41][42][43][44][45], to list the most prominent. Most of the reports on topology optimization in electromagnetics have focused on applications, including beamsplitters [18,19], photonic crystals [16,17], cloaks [20][21][22], sensors and resonators [44,45], metamaterials [23][24][25], excitation of surface plasmons [26], and electromagnetic and optical antennas [27][28][29]34], without presenting the systemical topology optimization methodology for electromagnetic waves in three-dimensional space.…”