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High-speed phase calibration method for large-scale silicon-based optical phased arrays.
Optics Express
|May 4, 2026
Summary
A new phase calibration method uses the Hadamard parallel gradient descent (HPGD) algorithm to significantly speed up optical phased arrays (OPAs). This HPGD approach reduces convergence iterations by up to 70% for faster, more efficient OPA calibration.
Area of Science:
- Photonics and Optical Engineering
- Signal Processing
- Integrated Circuits
Background:
- Large-scale optical phased arrays (OPAs) are crucial for applications like LiDAR and optical communication.
- Efficient and high-speed phase calibration is a key challenge for large-scale OPAs.
- Existing calibration methods can be slow and computationally intensive.
Purpose of the Study:
- To propose a high-speed phase calibration method for large-scale silicon-based OPAs.
- To improve the convergence speed and efficiency of OPA calibration.
- To demonstrate the effectiveness of the proposed method through simulations and experiments.
Main Methods:
- Integration of the Hadamard parallel gradient descent (HPGD) algorithm with a dedicated hardware architecture.
- Utilizing deterministic, orthogonal Hadamard matrices for efficient perturbation sequences.
- Employing a hardware architecture comprising an FPGA, DSP, and a high-speed avalanche photodiode (APD) for objective function acquisition.
Main Results:
- HPGD significantly reduces convergence iterations compared to stochastic parallel gradient descent (SPGD).
- A 512-element OPA showed a reduction from 4929 to 2285 iterations (HPGD) and 1480 iterations (adaptive gain variant, adaHPGD), a 70.0% improvement.
- For larger OPAs (1024–4096 elements), HPGD reduced iterations by 31.8%–41.3%.
- Experimental results on a 512-element OPA achieved a convergence time of 12.8 s with 6.7 ms per iteration.
- Calibrated beam achieved a peak sidelobe ratio of 12.93 dB and a full width at half maximum of 0.110°.
Conclusions:
- The proposed HPGD method offers a significant speed improvement for phase calibration of large-scale OPAs.
- The dedicated hardware architecture enables real-time, high-speed calibration.
- The method is effective for a wide range of OPA sizes, demonstrating scalability.
- Achieved calibration performance matches simulation results, validating the approach for practical applications.
