Abstract

Much of the analysis of high-power semiconductor-laser diodes that has been reported in recent literature is based on the assumption of uniform carrier density (and, consequently, on uniform gain) in the longitudinal direction (z-axis). It was noted long ago¹ however, that this assumption is inconsistent with the actual behavior inside the optical cavity. The differential equations that describe the carrier density and the optical fields inside the cavity are coupled, so that a nonuniform total optical field must of necessity introduce a nonuniform carrier density as a function of z. The assumption of uniform carrier density is reasonable for equal facet reflectivities, such as that determined by the GaAs-air interface, but becomes increasingly suspect for situations in which the reflectivities are different (for example, the extraction all optical power from one end in high-power applications) or in which fabrication techniques purposefully introduce variations on longitudinal pumping. To address these situations, an analysis that does not depend on the assumption of uniform carrier distribution is needed. This paper reports on efforts to analyze the behavior of semiconductor laser diodes, including possible variation of parameters in the z-direction. An iterative method has been adopted to examine analytically (to the extent possible) the nonuniformity of carrier density distribution. The first-order correction in the iterative solution is obtained by using two separate approaches. Numerical examples that illustrate the importance of this correction for asymmetric-cavity lasers will be presented.

© 1990 Optical Society of America