Highly-Linear and Wavelength-Tunable Frequency-Modulated Continuous-Wave Hybrid-Integrated Laser

Frequency-sweeping laser sources play a critical role in the accurate 3D mapping of frequency-modulated continuous-wave (FMCW) LiDAR systems, whose chirp linearity greatly impacts the measurement precision. Although various pre-distortion algorithms have been proposed to reduce chirp nonlinearity, these open-loop methods can rapidly suppress the chirp nonlinearity but they are susceptible to environmental variations and often exhibit subpar performance in long-range detection scenarios. In contrast, the electro-optical phase-locked loop (EO-PLL) serves as a real-time linearizing solution for FMCW LiDAR, enabling high-precision, high-resolution, and long-distance measurement capabilities. In this study, a III/V-Si3N4 hybrid-integrated external cavity laser (ECL) is used to generate an FMCW signal over a large wavelength tuning range of 68 nm. The maximum output optical power is 15.8 mW, and the intrinsic linewidth is 0.9 kHz. By modulating the phase shifter, an FMCW signal with a chirp bandwidth of 0.7 GHz is generated at a repetition rate of 1 kHz. The pre-distortion algorithm is combined with the gain-tunable EO-PLL system to suppress the chirp nonlinearity and frequency noise across multiple wavelengths, leading to a remarkable improvement in range precision from 202 to 4.2 cm when targeting a distance of 200 m. An InP/Si3N4 hybrid integrated ECL with a large wavelength tuning range and high chirp linearity is demonstrated by combining a pre-distortion algorithm with the EO-PLL technology. In this work, a gain-tunable EO-PLL system is implemented to generate the highly linear FMCW signal over the wavelength tuning range of 68 nm, providing remarkable improvements in range precision, resolution, and accuracy. image