Simulation of the generation of high-power pulses in the GHz range with three-section DBR lasers

The dynamical behaviour of three-section distributed Bragg reflected (DBR) lasers containing an active gain section and passive phase-shift and Bragg-grating sections was studied and modelled by numerically solving the travelling wave equations and a rate equation for the carrier density. By changing the parameters determining the optical gain or absorption, respectively, in the phase section a switching behaviour, hysteresis phenomena and self-sustained pulsations were obtained. By injecting small current pulses through the phase section, high-power optical pulses with small spectral width and repetition rates in the GHz range were generated. Experimentally, this was achieved by a selective heating of the phase section and by modulating the current injected into the phase section. In contrast to DBR lasers emitting at 1.3 μm and 1.55 μm, in the DBR lasers under investigation with an emission wavelength of 1.06 μm the active layer extends over all sections. Thus by the heating the interband absorption in the active layer of the phase section is strongly increased, while owing to the current pulses the absorption is rapidly reduced. Thus, giant light pulses are emitted which have a small spectral width owing to the wavelength selectivity of the Bragg grating