Photonics Breakthroughs 2024: Arbitrary Mode Manipulation Using Reconfigurable Integrated Photonic Processors

Optical modes offer spatial degrees of freedom that can be exploited to implement advanced functionalities across various applications. Conventional photonic devices used for the manipulation of modes operate on predetermined families of eigenmodes of specific systems. Here, we report on a recent finding of our research, where we demonstrate that reconfigurable photonic integrated circuits (PICs) can automatically identify optimal communication modes through arbitrary systems, always ensuring maximum achievable power transmission and mutual orthogonality. Such modes are determined in situ without any precalculation or prior knowledge of the system. Our results extend the concepts and the range of applications of existing schemes for mode manipulation to more complex functionalities and realistic scenarios. We also address recent related works on reconfigurable PICs for generation and detection of arbitrary, structured, and random beams, with an overview of the main results achieved on the different free-space and guided-waves technologies. A discussion of the main limits of the presented approach and the potential implications in diverse and emerging application fields is provided.