Inverse design of photonic integrated devices: Optimization and machine learning

The use of inverse design techniques is radically changing the way we conceive and design photonic integrated devices. Geometries with unprecedented complexity can take full advantage of modern fabrication technologies to demonstrate high performance and ultra-compact devices. This tutorial aims at exploring the fundamental concepts behind the use of both iterative optimization and machine learning approaches in the context of photonic design. Throughout the paper, we present the design of an integrated mode exchanger, chosen mainly as a pedagogical example, to highlight the specificity of the field, the advantages and disadvantages of the different design techniques, and to discuss the most important considerations that need to be made in choosing the right design tool.