Abstract

Self mode-locked (SML) quantum dash (QDh) lasers emitting at around 1550 nm are compact broadband optical frequency comb (OFC) sources for multi-wavelength communication applications [1,2]. Optical self-feedback (OFB) by auxiliary cavities with lengths in the meter-range is a well-established method for a precise and dynamical mode spacing control of passively mode-locked (PML) semiconductor lasers. Recent works focused on identifying maximum tuning ranges of quantum well PML lasers and suggested that external OFB length, interaction width of fed-back pulse with the pulse inside the laser cavity and the OFB strength appear predominant [3]. In this contribution, we experimentally investigate and explain by modeling the dependence of mode spacing of OFB of SML QDh lasers subject to different cavity lengths on the external optical delay. Here, we study the impact of different OFB strengths and external OFB cavity lengths onto the mode spacing of QDh SML lasers.

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