Reconfigurable spatial-mode generation and multiplexing on a scalable photonic chip

Spatial modes have found widespread applications in spatial division multiplexing (SDM), sensing, quantum information processing, and on-chip machine learning. The capability to manipulate multiple mode bases will greatly enhance versatility and accelerate the adoption of SDM by remaining agnostic to the specific mode types traversing optical networks. Programmable photonic integrated circuits offer compact and flexible control over spatial modes. In this work, we design and demonstrate a reconfigurable spatial mode generator utilizing a programmable silicon photonic chip. Our architecture leverages orbital angular momentum (OAM) modes as the basis to generate linear polarized (LP) modes and cylindrical vector (CV) modes, providing a scalable solution for spatial mode manipulation across amplitude, phase, and polarization domains. Using a proof-of-concept device, we experimentally generate ten distinct OAM modes and eight LP modes. Furthermore, we numerically analyze experimental errors and propose methods to enhance modal purity and enable effective vector mode generation.