Sub-10-kHz Linewidth Tunable DFB Laser Array via Self-Injection Feedback Technique

We propose and experimentally demonstrate tunable narrow-linewidth DFB laser array based on self-injection feedback Technique. The grating of the proposed tunable laser array is fabricated using the reconstruction equivalent chirp (REC) technique, which simplifies the grating fabrication process and improves wavelength precision. AR and HR coatings are applied to the front and rear facets of the lasers to enhance output power. The single-mode yield of the laser array is improved through the implementation of an asymmetric phase shift (APS). Additionally, the slab-coupled optical waveguide (SCOW) structure is employed to reduce linewidth and increase output power. Low-loss coupling between the laser array and the planar lightwave circuits (PLCs) is achieved via photonic wire bonding (PWB) technology. Finally, a wavelength-insensitive fiber optic circulator is used to further narrow the linewidth. Experimental results demonstrate that the proposed laser array achieves an output power exceeding 100 mW and a tuning range greater than 12.8 nm. When tuned with 100 GHz spacing, 16 wavelengths exhibit SMSRs greater than 50 dB. After passing through the optic circulator, the linewidth of the laser array is reduced to less than 7 kHz, approximately 1/50 of the original linewidth. The exceptional performance of the proposed laser array shows great promise as a tunable light source for coherent optical communication systems.