Optimization of photonic nanostructures

A Geometry Projection Method (GPM) for the optimization of photonic crystal nanostructures is used to improve the performance of two different photonic devices. The GPM is a level set based approach for defining a differentiable expression describing the material distribution of a structure. It gives direct control over areas of intermediate dielectric constant and implicit control over feature size, both key concerns for the design of nano-scale devices. The GPM, in conjunction with the finite element and adjoint methods, is used here to solve two different non-linear optimization problems. The diffraction from a two-dimensional photonic crystal waveguide termination is reduced, and the reflectivity of a three-dimensional photonic crystal laser cavity structure is increased. Significant improvements in both cases demonstrate that the GPM is an effective tool for optimization of photonic structures.