Compact polarization transformation-enabled on-chip delay line for frequency-swept laser nonlinearity calibration

Area of Science:

• Photonics
• Integrated Optics
• Optical Engineering

Background:

• On-chip optical delay lines are essential for advanced photonic integrated circuits.
• Applications include optical coherence tomography, optical gyroscopes, and FMCW LiDAR systems.
• Existing designs often face challenges with loss and compactness.

Purpose of the Study:

• To propose and demonstrate a novel low-loss and compact on-chip optical delay line.
• To integrate a polarization transformation-enabled 2-pass architecture.
• To validate its utility in nonlinearity calibration for FMCW LiDAR systems.

Main Methods:

• Designed a compact on-chip delay line using a silicon nitride waveguide spiral.
• Implemented a polarization transformation-enabled 2-pass architecture.
• Achieved a total delay of 10.46 ns with a 0.8-m waveguide length.

Main Results:

• Low losses achieved: 0.083 dB/cm (TE mode) and 0.213 dB/cm (TM mode).
• Successfully conducted nonlinearity calibration of a frequency-swept laser.
• Demonstrated significant enhancement in signal-to-noise ratio in an FMCW LiDAR system.

Conclusions:

• The developed on-chip delay line is compact and exhibits low loss.
• It effectively calibrates frequency-swept lasers, improving FMCW LiDAR performance.
• This work provides valuable insights for highly integrated FMCW LiDAR systems.