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Low-noise frequency-agile photonic integrated lasers for coherent ranging
Grigory Lihachev1, Johann Riemensberger1, Wenle Weng1,2
1Institute of Physics, Swiss Federal Institute of Technology Lausanne (EPFL), CH-1015, Lausanne, Switzerland.
Nature Communications
|June 20, 2022
Summary
This study presents a novel hybrid photonic laser for Frequency Modulated Continuous Wave (FMCW) LiDAR. It achieves a narrow linewidth and fast, agile tuning, enabling compact, high-performance ranging systems.
Area of Science:
- Photonics and Laser Technology
- Integrated Optics
- LiDAR Systems
Background:
- Frequency Modulated Continuous Wave (FMCW) LiDAR offers simultaneous distance, position, and velocity mapping with immunity to stray light and long-range capability.
- Existing integrated silicon-based lasers lack the fast nonthermal tuning (frequency agility) required for coherent ranging, despite advances in narrow linewidths.
- The precise chirping of narrow linewidth, low-noise lasers is crucial for FMCW LiDAR performance.
Purpose of the Study:
- To demonstrate a hybrid photonic integrated laser with both ultra-narrow intrinsic linewidth and fast frequency agility.
- To develop a compact coherent LiDAR engine capable of generating high-performance FMCW chirp signals.
- To overcome the limitations of current integrated lasers for advanced LiDAR applications.
Main Methods:
- Utilized ultralow-loss Si3N4 photonic microresonators and MEMS-based stress-optic actuation (AlN or PZT).
- Employed self-injection locking of an Indium Phosphide (InP) laser chip for low-phase-noise lasing.
- Implemented difference-drive and apodization techniques to suppress mechanical vibrations and achieve a flat actuation response.
Main Results:
- Demonstrated a hybrid photonic laser with a 25 Hz intrinsic linewidth and 1.6 × 10^15 Hz/s tuning speed over 1 GHz.
- Achieved a compact coherent LiDAR engine generating 800 kHz FMCW triangular optical chirp signals without linearization or predistortion.
- Successfully performed a 10 m optical ranging experiment with a resolution of 12.5 cm.
Conclusions:
- The developed hybrid photonic integrated laser system meets the requirements for high compactness, fast frequency actuation, and spectral purity in LiDAR.
- This technology advances the development of next-generation coherent LiDAR systems for various applications.
- The approach leverages foundry-based technologies for scalable and cost-effective manufacturing.
