Abstract

We will show in this paper that the relevant semiconductor gain medium properties giving rise to spatial and temporal instabilities are the differential gain and refractive index, dG/dN and dδn/dN, respectively. The latter is often replaced by the antiguiding or linewidth enhancement factor, α= K₀(dδn/dN)/(dG/dN), where K₀ is the laser field wave vector in vacuum. A purpose of our paper is to point out the relationships among G,dG/dN, dδn/dN, and α. Owing to these relationships, the common practice of treating these quantities as independent parameters in the modeling of semiconductor lasers is inconsistent. On the other hand, the experimentally obtainable combinations of G, dG/dN, dδn/dN, and αcover a very wide range of situations. This is because one has the choice of bulk and quantum well gain media, and for a quantum well medium, present growth techniques make available a wide range of well widths and strains. This flexibility makes the semiconductor laser an excellent tool for studying laser instabilities. We will use a gain model, which contains the many-body carrier-carrier interactions and the band mixing effects due to quantum confinement and strain, to illustrate the different experimental conditions reachable with a semiconductor laser. As an example, we will present the results of our investigation on the behavior of a vertical cavity surface emitting laser (VCSEL) in the presence of an injected optical field, where we observed relaxation oscillation, sub-harmonic bifurcation, and chaos under certain operating conditions.

© 1992 Optical Society of America