Nonparametric design of nanoparticles with maximum scattering using evolutionary topology optimization

Abstract

• A free form nanoparticle is designed for maximum scattering using topology • optimization. • The optimization objectives increased 2-35 times compared to standard shapes. • Spectral cross sections increased between 1-10 times compared to standard shapes. • A checkerboard control scheme is proposed in addition to the filtering techniques. The interaction between light and subwavelength structures provides tailorable optical properties that can be useful in many engineering applications. These properties strongly depend on the material shape, which provides obtaining unique scattering characteristics when rigorously designed. However, the conventional design methods require precise modeling and characterization of the shapes of the scattering objects, thus requiring a lot of intuition and knowledge about light radiation at small scales, as well as many rounds of experimental trial and error. We propose a framework to discover new nanoparticle designs for improved scattering based on topology optimization. The framework allows us to maximize the scattering cross section of the particle domain. Increased scattering cross-section at nanoscale leads to improved light trapping, which is critical in many applications such as thin film solar cells and biological imaging. Topology optimization offers a knowledge independent design procedure, therefore revealing relationships between specific regions in the design domain and the light behavior for maximum scattering cross section.