Shifted rectangular mesh architecture for programmable photonics

Abstract: Programmable integrated photonics has evolved into a potent platform for implementing diverse optical functions on a single chip through software-driven reconfiguration. At the core of these processors are the photonic waveguide meshes that enable flexible light routing and manipulation. However, recirculating hexagonal waveguide meshes, which currently constitute the basic component of the mesh, are essentially limited by the fixed dimensions of their elementary cells, which consist of as many as six components, limiting their spectral and temporal resolution. These limitations have a detrimental effect on the processing of broadband signals and the application of high-precision delay lines. Here, we introduce the concept of shifted rectangular waveguide mesh architecture for programmable photonics by shifting the adjacent columns or rows by a certain specific value. The operation of these shifted rectangular cells is predicated on the rectangular shape of the cell, which is associated with a smaller number of tunable basic units (TBUs), i.e., four, compared to cells based on a hexagonal mesh, i.e., six. However, at the same time, they allow the signal to be redirected to the input port, which distinguishes them from the regular square mesh-based structure. This approach unlocks new degrees of freedom in programmable photonic circuits, offering enhanced spectral and temporal tunability. Additionally, it paves the way for advanced application in topological photonics, quantum information processing, neuromorphic and high-speed optical computing. The photonic chip arranged in this architecture is capable of implementing one or multiple simultaneous photonics circuits with optical feedback paths and/or linear multiport transformations by the appropriate programming of its resources and the selection of its input and output ports.