Photonic integrated processor for structured light detection and distinction

Integrated photonic devices are pivotal elements across research fields that involve light-based applications. Particularly versatile platforms are programmable photonic integrated processors, which are employed in applications like communication or photonic computing. Free-space distributions of light can be coupled to such processors, which subsequently control the coupled light on-chip within meshes of programmable optical gates. This enables access to the spatial properties of free-space light, particularly its relative phase, which is usually challenging to measure. Here, we discuss and show the detection of amplitude and phase distributions of structured higher-order light beams using a multipurpose photonic processor. This can be used to directly distinguish light’s orbital angular momentum without including additional elements interacting with the free-space light. We envision applications in a range of fields that rely on the spatial distributions of light’s properties, such as microscopy or communications.