Passive mode-locked pulses with repetition frequencies in the range 40 to 90?GHz were observed in blue-violet GaN-based quantum-well lasers without external cavities. The lasers had two-section geometry with built-in saturable absorber section. The individual pulses had durations as short as 3–5 ps at peak powers of around 320 mW.
Applied Physics Letters, vol. 102 (12), pp. 121115