Broadband 100 GHz Frequency Comb From an Asymmetric MQW Passively Mode-Locked Laser

We report a passively mode-locked AlGaInAs/InP laser diode based on an asymmetric multiple quantum well structure, designed for 100 GHz optical frequency comb generation near $1.5~\mu $ m. The active region comprises quantum wells with two different photoluminescence wavelengths by using different thicknesses but identical material composition, optimized to enhance spectral overlap and broaden the modal gain profile. The device delivers a −3 dB optical bandwidth of 10.14 nm, spanning 14 lines with a spacing of 0.78 nm. To the best of our knowledge, this is the widest bandwidth reported from any directly electrically pumped quantum-well passively mode-locked laser diode. These results demonstrate a compact and practical approach to generating wideband optical frequency combs using asymmetric multiple quantum well mode-locked laser diodes.