Highly linear directly modulated DFB laser towards pre-distortion-free FMCW LiDAR

Area of Science:

• Photonics and Optical Engineering
• Laser Technology
• Sensing and Measurement

Background:

• Frequency-modulated continuous wave (FMCW) LiDAR requires highly linear frequency sweeps for accurate measurements.
• Existing laser sources often suffer from nonlinearities, necessitating complex pre-distortion techniques.
• Two-section distributed feedback (DFB) lasers are potential candidates for FMCW LiDAR due to their tunability.

Purpose of the Study:

• To develop and characterize a highly linear two-section distributed feedback (DFB) laser for FMCW LiDAR applications.
• To achieve pre-distortion-free operation, simplifying LiDAR system design and improving performance.
• To demonstrate the feasibility of using this laser for accurate range and velocity measurements.

Main Methods:

• Fabrication of a two-section DFB laser.
• Characterization of laser performance, including frequency excursion, chirp nonlinearity, output power, side-mode suppression ratio (SMSR), and intrinsic linewidth.
• Proof-of-concept experiment to demonstrate range and velocity measurements using the developed laser.

Main Results:

• The DFB laser achieved a frequency excursion of 2.9 GHz.
• Chirp nonlinearities were as low as 0.65% (up-ramp) and 0.28% (down-ramp).
• The device delivered 40 mW output power with a 42 dB SMSR and a 586 kHz intrinsic linewidth, without pre-distortion.

Conclusions:

• The developed two-section DFB laser exhibits excellent linearity, suitable for pre-distortion-free FMCW LiDAR.
• The laser's performance metrics meet the requirements for high-accuracy range and velocity sensing.
• This work paves the way for simpler and more efficient FMCW LiDAR systems.