Programmable Integrated Silicon Photonics Waveguide Meshes: Optimized Designs and Control Algorithms

Programmable Integrated Photonics is a recent area of research that aims to integrate a very-large scale of reconfigurable photonic components to enable flexible and versatile photonic integrated circuits. In this paper, we review the state of the art of general-purpose waveguide mesh arrangements with a special focus on those that allow the synthesis of optical feedback loops. Moreover, we propose for the first time, a new design approach to generate waveguide mesh patterns with equally-oriented components. This innovation is of special relevance to improve performance and to mitigate one of the main scalability limitations, the integration density. The paper finalizes with an introduction to control algorithms for waveguide mesh arrangements based on derivative methods and non-derivative methods. These control methods provide a proof for the self-reconfiguration of large-scale waveguide mesh arrangements. In particular, we apply the computational optimization algorithms to program a hexagonal waveguide mesh to emulate a 1 x 8 beamforming network and an optical filter based on an unbalanced MZI design. All in all, the paper comprises recipes to achieve truly practical software-defined photonic integrated circuits.