Timing stability and repetition rate frequency tuning analysis of a passively mode-locked multiquantum well semiconductor laser subject to dual cavity optical self-feedback
Monolithic passively mode-locked (PML) semiconductor lasers with multi-GHz repetition rate (RR) emitting at wavelengths of around 1070nm are attractive ultrafast sources for seeding ytterbium doped fiber amplifiers and for photonic communication at high data rates. The timing stability quantified by the timing jitter (TJ) and the RR tuning range of a PML multi quantum-well (QW) semiconductor laser emitting at 1070nm subject to dual-cavity optical self-feedback (DC-OFB) consisting of one very short cavity for a high RR tuning range and one very long cavity for strong TJ reduction is investigated. The 3mm long PML QW semiconductor laser with a saturable absorber section length of 10% of the total cavity length has a RR of 13.61 GHz and a TJ of 83 fs with a pulse width amounting to 8 ps at the investigated injected gain current, absorber reverse bias voltage and cooling block temperature. For the combination of the long fiber-based cavity amounting to 5.9m combined with the short free-space cavity amounting to a few laser cavity lengths a RR tuning range over 1 GHz is achieved. Furthermore a minimal TJ of approximately 330 as with full sideband suppression in the radio-frequency (RF) spectrum is achieved which is an improvement by factor 250 in comparison to the free-running laser.