Ultra-Fast Broadband Wavelength-Swept DFB Laser Array with 400 kHz Sweep Rate and 60 nm Continuous Tuning Range

Fast broadband wavelength-swept lasers (WSLs) are core components in optical sensing fields such as fiber Bragg grating (FBG) sensing and optical coherence tomography. This work presents a novel WSL based on a distributed feedback (DFB) laser array combined with enhanced self-heating effects, achieving a 400 kHz sweep rate and a continuous (gap-free) wavelength tuning range of 60 nm, with a tuning speed exceeding 24 nm/μs. To the best of our knowledge, this work achieves the highest sweeping frequency reported for broadband (>30 nm) WSLs based on DFB laser arrays up to now. The reconstruction-equivalent-chirp technique simplifies grating fabrication and improves the accuracy of wavelength interval control, with the wavelength error measured to be within ±0.2 nm. Reducing the doping concentration in the p-waveguide region enhances the self-heating effect, enabling a continuous tuning range of over 5 nm per channel. The DFB laser array exhibits side-mode suppression ratios >45 dB, output power >55 mW, and relative intensity noise below −130 dB/Hz. The proposed WSL was successfully applied in an FBG sensor interrogation system, where the wavelength fluctuation over 5000 continuous interrogation cycles was less than 2 pm (within ±1 pm), demonstrating outstanding wavelength sweeping repeatability. In temperature measurement experiments (−30 to 90 °C) and strain measurement experiments (−800 με to 800 με), the interrogation linearity of all FBG sensors was greater than 0.9993. In vibration measurement experiments, the system successfully measured high-frequency vibration signals at 45 kHz, 85 kHz, and 128 kHz, with an acquisition time resolution of 2.496 μs. This work provides a new direction for the development of high-speed broadband WSLs.