Optical Injection-Induced Timing Jitter Reduction in Gain-Switched 1550-nm Discrete Mode Semiconductor Lasers

Advanced laser modulation techniques have enabled the development of versatile and efficient light sources for quantum communications [1]. In fact, semiconductor lasers are normally used as single-photon sources in most commercial and research quantum key distribution (QKD) systems [2]. In particular, modulated single-mode semiconductor lasers, utilizing gain-switching, optical injection locking and direct phase modulations have been used to implement a great variety of QKD protocols [1]. In recently introduced protocols, like the measurement-device-independent one (MDI) based on the interference of pulses generated by two remote semiconductor laser sources, timing-jitter in gain-switched lasers affects the temporal overlap of the pulses producing a dramatic reduction in the interference visibility [1]. Very recently MDI-QKD systems using optical injection from a semiconductor laser into a gain-switched semiconductor laser have been demonstrated [1]. A reduction of timing-jitter induced by optical injection is then desirable to improve the interference visibility in this type of MDI-QKD systems.