Universal photonic processor for spatial mode decomposition

Efficient and precise information storage and processing using light's various degrees of freedom - intensity, phase, and polarization - have vast applications in modern photonics. The corresponding utilization necessitates the accurate measurement and decomposition of arbitrary spatial modes into their orthogonal components. In this paper, we introduce a new modal decomposition technique based on a 16-pixel reconfigurable photonic integrated circuit programmed as a spatial mode decomposer. This device uniquely identifies and quantifies the relative contributions of constituent modes in a Laguerre-Gaussian basis. The presented device not only provides the relative weights of these modes but also their relative phases, offering a novel approach based on an integrated platform for optical information processing. We further highlight a novel input interface that enables the decomposition of input beam polarization into circular polarization basis. The potential applications of this technology are vast, ranging from advanced optical communications to microscopy and beyond, marking a significant stride in the field of integrated photonics.