Optimized photon routing with a silicon 3 × 3 waveguide coupler device

In integrated photonics, the precise control and routing of light signals is crucial. Conventionally, light routing in photonic devices is achieved using multi-mode interferometers and microresonators. An alternative approach is to use n × n waveguide couplers. In this study, we explore the use of such devices both theoretically and experimentally in the realization of a versatile 3 × 3 coupler on the silicon photonics platform. We demonstrate that this device can effectively route signals in multiple ways: crossing signals between the external waveguides for a specific coupling, or distributing signals evenly across the three output waveguides, as well as functioning as a versatile switch for other arbitrary output combinations. By fitting the experimental results with a theoretical model, we extracted its characteristic parameters, highlighting both the model's behavior and the impact of non-idealities. Our work lays the foundation for the design of an efficient and tunable 3 × 3 waveguide coupler device.