Demonstration of a directly modulated laser achieving bandwidth exceeding 50 GHz with an integrated active feedback waveguide

With the significant expansion of communication capacity in fiber-optic networks, the directly modulated laser serves as a viable candidate due to its low cost and small footprint. In recent years, distributed feedback (DFB) lasers with an integrated passive feedback waveguide were demonstrated to enhance bandwidth by introducing a photon-photon resonance or detuned-loading effect. However, the butt-joint regrowth process between the active layer and passive waveguide complicates the fabrication. Here we propose and demonstrate a DFB laser with an integrated active feedback waveguide, utilizing identical active layer technology to simplify the fabrication process, achieving a bandwidth of exceeding 50 GHz. Additionally, transmission experiments with 55 Gbps NRZ and 70 Gbps PAM4 signals are also demonstrated. (c) 2024 Chinese Laser Press