Extremely low-amplitude modulation in a subharmonically hybrid mode-locked monolithic semiconductor laser

Negligibly small amplitude modulation and sufficiently low timing jitter are achieved simultaneously in a passively mode-locked monolithic semiconductor laser stabilized by applying an electrical signal at the second subharmonic of the pulse repetition frequency. Nearly transform-limited 33 GHz pulse trains with 0.56 ps timing jitter and -23 dBc amplitude modulation are obtained with 23 dBm driving signals at 16.5 GHz. Detailed investigations are carried out on the dependence of the amplitude modulation and timing jitter on RF driving power for the second- and third-order subharmonic cases. The excellent amplitude modulation property of the second subharmonic case with the specific laser used in this work is ascribed to the frequency response characteristics of the device.