Self-Sustained Picosecond Optical Pulse Generation From Laser Diodes

Abstract

Generation of short optical pulses at gigabit rate from laser diodes has been demonstrated by several techniques. These includes gain switching, mode locking, optoelectronic feedback, and mutual phase-locked loop. In this paper we present an alternative technique to obtain self-sustained operation of semiconductor laser diodes generating picosecond optical pulses. The short pulse train is obtained forcing the laser into the relaxation oscillation. As the laser is turned on fast enough, it emits short optical pulses of decaying amplitudes. A replica of oscillation will also be present on the laser current and the electrical circuit. By implementing a wideband electronic gain media in the laser circuit, the current transient can be amplified and returned to the laser. The amplified feedbacked signal is phased so that it enhances the laser gain which, after a few cycle of growing transient, produces steady-state repetitive optical pulses. The system is then, effectively, an optoelectronic oscillator reaching steady state operation after an initial imposed transients. Experimental results on the performance of Gb/s picosecond optical pulse generator for high speed data communication system will be presented. Circuit arrangement of a compact self-sustained pulse generator suitable for an integrated optoelectronic circuit will be discussed.