Phase noise reduction of passively mode-locked quantum-well semiconductor lasers by dual-cavity optical self-feedback

Passively mode-locked semiconductor lasers emitting picosecond short optical pulses at multi-GHz repetition rates and at wavelengths of around 1070 nm are attractive sources for seeding ytterbium doped fiber amplifiers or future data telecom. We present a 3 mm long passively mode-locked quantum-well semiconductor laser emitting 8.6 ps short optical pulses at a repetition rate of 13.6 GHz. By subjecting the laser to dual-cavity optical self-feedback by both a short external passive cavity and a long external passive cavity, phase noise reduction and repetition rate control is studied experimentally. Such a dual-feedback scheme allows simultaneously for a strong repetition rate tuning range as well as a strong phase noise reduction. A maximum repetition rate tuning range exceeding 1 GHz as well as repetition rate multiplication up to 54.4 GHz, the fourth harmonic mode-locking order, is presented. A timing jitter improvement by a factor of 200 is demonstrated.