Pulse characteristics of passively mode-locked quantum dot lasers

Interest in quantum dot mode-locked lasers (QD MLLs) has grown in recent years since their first demonstration in 2001 as applications for optical time domain multiplexing, arbitrary waveform generation, and optical clocking are anticipated. Ultrafast pulses below 1 ps have been reported from QD MLLs using intensity autocorrelation techniques, but so far detailed characterization examining the pulse shape, duration, chirp, and degree of coherence spiking in these lasers has not been carried out. We describe the first direct frequency-resolved optical gating (FROG) measurements on a QD MLL operating at a repetition rate of 5 GHz.