Interferometric imaging using Si₃N₄ photonic integrated circuits for a SPIDER imager.

Area of Science:

• Photonics
• Optical Engineering
• Interferometry

Background:

• Photonic integrated circuits (PICs) are crucial for advanced optical systems.
• Interferometric imaging requires precise control over optical path differences.
• Broadband interference measurements are essential for high-resolution imaging.

Purpose of the Study:

• To design, fabricate, and demonstrate a silicon nitride PIC for interferometric imaging.
• To achieve one-dimensional interferometric imaging with twelve baselines.
• To enable two-dimensional complex visibility measurements.

Main Methods:

• Fabrication of a silicon nitride PIC with twelve waveguide pairs and multi-mode interferometers (MMIs).
• Integration of an 18-channel arrayed waveguide grating (AWG) for spectral separation.
• Construction of a testbed for two-dimensional complex visibility measurements.
• Maintaining optical path difference (OPD) within 1 µm for maximal fringe visibility.

Main Results:

• The PIC successfully generated broadband interference fringes across twelve baselines near 1100-1600 nm.
• A total of 103 sets of fringes were collected by the detector array.
• Reconstructed images from two-dimensional measurements showed good agreement with theoretical predictions.

Conclusions:

• The developed silicon nitride PIC is effective for high-precision interferometric imaging.
• The system demonstrates capabilities for both 1D and 2D complex visibility measurements.
• This work advances PIC technology for applications in optical metrology and imaging.