AlGaInAs quantum-well lasers with semi-insulating buried-heterostructure for high-speed direct modulation up to 40 Gbps

We introduce our recent works on directly-modulated AlGaInAs quantum-well lasers with semi-insulating buried-heterostructure for ultra-high-speed transmission. The short-cavity 1.3-µm-wavelength DFB lasers showed low-penalty transmission up to 13 km under direct modulation at 25 Gbps, as well as clearly-opened eye patterns by 40-Gbps direct modulation. For further reduction of driving current in the high-speed directly-modulated lasers, we developed the distributed reflector lasers with the active-region having the length of 100 µm or less, sandwiched by the passive reflectors. The fabricated distributed reflector lasers exhibited very high slope value of relaxation oscillation frequency of 4.0 GHz/mA^½ and more. The distributed reflector lasers emitting in 1.3-µm wavelength region achieved 40-Gbps direct modulation with the driving current of 2/3 of that by the DFB lasers. By the distributed reflector lasers of 1.55-µm-wavelength, high temperature 40-Gbps operation was realized as well as reduction of driving current.