Mode-Locked DBR and DFB Lasers With Multiple Phase-Shifted Gratings for THz Generation

We propose mode-locked distributed Bragg reflector (DBR) and distributed feedback (DFB) lasers based on multiple phase-shift gratings (MPSGs) for terahertz (THz) signal generation, with the latter incorporating an equivalent π-phase shift. By integrating optimized MPSGs, we achieve multi-channel lasing with uniform reflectivity and dense channel spacing. Mode-locked DBR lasers operating at THz frequencies of 150 GHz, 400 GHz, 800 GHz, and 1.2 THz have been demonstrated, as confirmed by second harmonic generation measurements. Additionally, a 200 GHz mode-locked DFB laser was realized. Amplified by an erbium-doped fiber amplifier (EDFA), the mode-locked DFB laser output was injected into a photoconductive antenna (PCA) to generate THz signals, with the measured power reaching 19.6 μW. These results highlight the potential of MPSG-based mode-locked lasers for compact and efficient THz generation systems.