Passive silicon nitride integrated photonics for spatial intensity and phase sensing of visible light

Phase is an intrinsic property of light, and thus a crucial parameter across numerous applications in modern optics. Various methods exist for measuring the phase of light, each presenting challenges and limitations-from the mechanical stability requirements of free-space interferometers to the computational complexity usually associated with methods based on spatial light modulators. Here, we utilize a passive photonic integrated circuit to spatially probe phase and intensity distributions of free-space light beams. Phase information is encoded into intensity through a set of passive on-chip interferometers, allowing conventional detectors to retrieve the phase profile of light through single-shot intensity measurements. Furthermore, we use silicon nitride as material platform for the waveguide architecture, facilitating broadband utilization in the visible spectral range. Our approach for fast, broadband, and spatially resolved measurement of intensity and phase enables a wide variety of potential applications, ranging from microscopy to free-space optical communication.