Mode locking of a semiconductor laser by self-synchronising optoelectronic feedback of the longitudinal mode beats

It is demonstrate that mode locking of an external cavity GaAs/(GaAl)As semiconductor laser can be achieved by regenerative feedback of the amplified RF beats of the longitudinal modes detected by a fast photodetector. Stable pulse trains with 10 to 40 ps pulsewidth are generated by careful adjustment of DC bias, amplification of the electronic feedback and optoelectronic delay. Results are presented which explore the capability of this new mode locking technique for the generation of pulse codes for future OTDM systems.