Optical phased array with on-chip phase calibration

Area of Science:

• Photonics
• Integrated Optics
• Beamforming Technology

Background:

• Robust beamforming in optical phased arrays (OPAs) requires precise phase monitoring and control.
• Existing calibration methods can be complex and computationally intensive.

Purpose of the Study:

• To demonstrate an on-chip integrated phase calibration system for high-fidelity beam steering in OPAs.
• To enable linear complexity calibration and arbitrary optical beam generation.

Main Methods:

• Fabrication of a 32-channel OPA with a 2.5-µm pitch using an Si-SiN photonic stack.
• Integration of compact phase interrogator structures and silicon photon-assisted tunneling detectors (PATDs) for readout.
• Implementation of a model-based calibration procedure for phase-error correction.

Main Results:

• Achieved high-fidelity beam steering with a sidelobe suppression ratio (SLSR) of -11 dB.
• Demonstrated a beam divergence of 0.97° × 0.58° at a 1.55-µm wavelength.
• Successfully performed wavelength-dependent calibration for full 2D beam steering and arbitrary pattern generation.

Conclusions:

• The developed on-chip calibration system significantly enhances OPA performance for beamforming applications.
• The integrated approach offers a low-complexity solution for accurate phase control and versatile beam generation.
• The use of PATDs allows for sub-bandgap light detection without additional fabrication steps.