InP femtosecond mode-locked laser in a compound feedback cavity with a switchable repetition rate

A monolithically integrated mode-locked semiconductor laser is proposed. The compound ring cavity is composed of a colliding pulse mode-locking (ML) subcavity and a passive Fabry-Perot feedback subcavity. These two 1.6 mm long subcavities are coupled by using on-chip reflectors at both ends, enabling harmonic mode locking. By changing DC-bias conditions, optical mode spacing from 50 to 450 GHz is experimentally demonstrated. Ultrafast pulses shorter than 0.3 ps emitted from this laser diode are shown in autocorrelation traces.European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 642355 FiWiN5G, Spanish Ministerio de Economia y Competitividad DiDACTIC project (TEC2013-47753-C3-3-R), and Consejería de Educación, Juventud y Deporte of Comunidad de Madrid DIFRAGEOS project (P2013/ICE-3004)