Mode locking of individual array modes of a gain-guided single-quantum-well laser array with an external mirror

Mode locking of individual spatial lateral array modes of gain-guided GaAs single-quantum-well laser array with an external mirror is observed. The single-lobe fundamental array mode and several higher order array modes were individually selected by adjusting the external mirror. The array modes were characterized by the far-field patterns of the laser array. The corresponding spectrum consists a number of narrow longitudinal modes indicating that a single array mode was selected. These array modes were mode locked using a combination of feedback from the external mirror and sinusoidal RF modulation. The far-field patterns remained spatially constant when the RF modulation was applied. Autocorrelation pulsewidth measurements showed that the pulses have a Gaussian shape. Pulses as short as 70 ps were obtained for the lowest order array mode, where all the laser emitters were in phase, and increase with increasing array mode order.