Radio-frequency analysis of self-mode-locked quantum dot laser

We numerically study and confirm experimentally a transition from unlocked multi-modal emission to self-mode-locked emission of a single-section InAs/InGaAs quantum dot laser in dependence on the laser injection current. At this transition, the radio-frequency beat note linewidth as well as the modal power fluctuations quantified by an integrated relative intensity noise of all modes are found to be significantly reduced. A linewidth reduction from several hundreds of MHz to below 1 MHz is observed, with the lowest value observed being as small as 20 kHz. Experiment and simulation results are in good qualitative and quantitative agreement.