Dynamic characteristics of phase-locked multiple quantum well injection lasers

The first streak-camera measurements of the fast pulse response of phase-locked, multiple quantum well diode laser arrays are reported. The time evolution of the emission during a single pulse and averaged over multiple pulses has been measured in both the near field and far field. Single-pulse traces of the intensity emitted by individual stripes in the array exhibit strong spikes 100-200 ps in duration at a repetition period of 300-400 ps. Simultaneous recording of the single-pulse emission from adjacent emitters shows near perfect correlation between the spiking of adjacent stripes. However, the spikes are less prominent in the single-pulse emission of the entire array. Multiple pulse averages of the emission from individual stripes exhibit synchronous relaxation oscillations persisting for a few nanoseconds at gigahertz frequencies and thereafter are smooth indicating random phasing of the spikes seen in the single-emitter single-pulse emission. The time evolution of far field suggests that phase-locking is established within 100 ps of the initiation of lasing. The evolution of the near- and far-field patterns is consistent with lasing in supermodes of the array.