Inverse Design of Photonic Crystals through Automatic Differentiation

• DOI: 10.1021/acsphotonics.0c00327
• Publication Date: 2020-06-09T22:04:20Z
• Authors: Momchil Minkov; Ian A. D. Williamson; Lucio C. Andreani; Dario Gerace; Beicheng Lou; Alex Y. Song; Tyler W. Hughes; Shanhui Fan
• Keywords: Automatic differentiation; Plane wave expansion; Waveguide

Gradient-based inverse design in photonics has already achieved remarkable results designing small-footprint, high-performance optical devices. The adjoint variable method, which allows for the efficient computation of gradients, played a major role this success. However, gradient-based optimization not yet been applied to mode-expansion methods that are most common approaches studying periodic structures such as photonic crystals. This is because, simulations, method cannot be defined explicitly standard finite-difference or finite-element time- frequency-domain methods. Here, we overcome gap through use automatic differentiation, generalization arbitrary computational graphs. We implement plane-wave expansion and guided-mode using an differentiation library, show gradient any simulation output can computed efficiently parallel, with respect all input parameters. then implementation optimize dispersion crystal waveguide, quality factor ultrasmall cavity lithium niobate slab. extends entirely new class more broadly highlights importance could play future tracking optimizing complicated physical models.