Passive mode locking of monolithic semiconductor ring lasers at 86 GHz

We report the development of monolithic passively mode-locked semiconductor ring lasers. These direct-waveguide-coupled lasers with a ring radius of 150 μm emit a continuous train of 1.3 ps transform-limited lasing pulses at 86 GHz repetition rate with a peak power of 10 mW/pulse at the laser output facet. We also observe, under certain conditions, the presence of a second pulse in the ring cavity doubling the pulse repetition rate to 172 GHz.