Robust all-optical harmonic clock signal generation through optical injection into passively mode-locked semiconductor lasers

In this paper, we demonstrate all-optical harmonic clock signal generation, in a passively mode-locked semiconductor laser, through optical injection of pseudorandom optical pulses, with a repetition rate at a subharmonic of the laser´s cavity frequency. The locking dynamics are characterized in terms of injected bit patterns. It is shown that the laser is a very robust clock signal generator at 38 GHz (timing jitter of less than 0.4 ps with 2/sup 31/-1 pseudorandom binary sequence (PRES) injection at the 20th subharmonic). It also can withstand extreme injection conditions (PRES mark ratio as low as 1/8) at the 20th subharmonic at an injection power of -3 dBm.