Investigation of Programmability in MZI-based Clements Meshes for Photonic Logical Operations

In this work, we analyze the impact of the Coupling Layer (CL) topology on the operation of a 3 × 3 mesh of Mach-Zehnder Interferometers (MZIs) in Clements configuration, when employed to implement user-defined logical operations. By adopting a Genetic Algorithm (GA)-based optimization method, we determine optimal phase shifts for each MZI in the Clements mesh to achieve a specific logical operation, given a fixed CL topology. We investigate device programmability based on numerical simulation using both the Extinction Ratio (ER) and the Threshold Ratio (TR) metrics, demonstrating that some CL topologies can support more than 80% of all possible truth tables with an ER greater than 3 dB. We analyze in detail the device programmability based on a case study of a specific CL topology with good ER performance, finding that it can implement at least 16 Boolean functions with an ER greater than 5 dB. These results provide insights for photonic chip design and testing.