Topological nano-aperture configuration by structural optimization based on the phase field method

This study is proposed in order to expand the topology optimization application to the metallic structure design in electromagnetic fields at very small wavelength, i.e., equal or less than the infra-red wavelength range. The phase field method based structural optimization combined with the double well potential is adopted in the optimization process for updating design variables not only to avoid gray scale representation but also to obtain simplified structure by controlling the diffusion coefficient. To define the material distribution of a design domain composed of metallic material, the electromagnetic energy in the design domain located between the dielectric and the metal layer is computed considering the surface plasmon effect. A numerical example is given to design the optimal cross sectional shape of a vertical-cavity surface-emitting laser system to maximize transmission efficiency and results are compared for various conditions.