Abstract

Gain-coupled (GC) distributed feedback (DFB) semiconductor lasers have been found to possess dynamic characteristics different from those of conventional DFB lasers. They sometimes give us useful properties such as enhanced small signal modulation bandwidth¹ and smaller linewidth enhancement factor.² Most of all, their capability of generating nearly-transform- limited optical short pulses by simple gain switching configuration^3-5 is very advantageous for soliton transmission systems. In order to clarify how this uncommon feature is embodied, we have observed, for the first time, temporally-dispersed spectra of the optical short pulses generated from GC DFB lasers of absorptive grating type. Measured pump dependence of chirp direction has indicated that their photon- density-dependent absorption plays a key role in producing the low chirping optical pulses.

© 1994 Optical Society of America