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. Extending this capability, spatial structuring of light offers an orthogonal set of mode families, represented within an infinite-dimensional Hilbert space. 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. 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.