Abstract

Contrary to solid state mode-locked lasers where technical noises (cavity length fluctuation and pump noise) are predominant, passively mode-locked semiconductor lasers are submitted to a large level of quantum noise originating from the spontaneous emission in the cavity. RF linewidth of passively mode-locked semiconductor laser has been the subject of recent experimental studies [1] showing that the repetition rate of the laser exhibits on a large frequency span a Lorentzian spectrum whose linewidth decreases with the inverse of the internal optical power, which shows that the repetition rate is dominated by quantum noise. Optical linewidth of longitudinal modes in actively mode-locked diode lasers has been shown experimental to be constant [2]. However, no experimental results have been reported for passive mode-locking.

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