We measured the optical linewidths of a passively mode-locked quantum dot laser and show that, in agreement with theoretical predictions, the modal linewidth exhibits a parabolic dependence with the mode optical frequency. The minimum linewidth follows a Schawlow-Townes behavior with a rebroadening at high power. In addition, the slope of the parabola is proportional to the RF linewidth of the laser and can therefore provide a direct measurement of the timing jitter. Such a measurement could be easily applied to mode-locked semiconductor lasers with a fast repetition rate where the RF linewidth cannot be directly measured.
Bibliographical note© 2009 Optical Society of America
T. Habruseva, S. O'Donoghue, N. Rebrova, F. Kéfélian, S. P. Hegarty, and G. Huyet, "Optical linewidth of a passively mode-locked semiconductor laser," Optics letters, 34, 3307-3309 (2009)
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