Fig. 2: Illustration of the experimental setup to measure higher-order beams.
From: Photonic integrated processor for structured light detection and distinction
a Input beams are weakly focused onto the free-space interface of the photonic processor where they couple to on-chip waveguide modes which are processed on-chip in a mesh of interferometers while transmitted intensities are recorded off-chip by imaging the monitoring interface. b, c Ultimately, not only amplitude but also the phase information of the input beams is measured at each grating coupler position.
