Topology optimization in nonlinear nanophotonics: from frequency conversion to exceptional points

We apply a large-scale inverse design strategy based on topology optimization (TO) toward the automatic discovery of complex nanophotonic structures—new kinds of micropillars, photonic-cyrstal slabs, and waveguides comprising complicated arrangements of subwavelength dielectrics—exhibiting unusual nonlinear and spectral properties. The structures support multiple, tightly confined resonances at far-away wavelengths and exhibit the largest...