Theoretical derivatives of the electrical characteristic of a junction laser operated in the vicinity of threshold

Analytic expressions are derived to describe the ideal electrical behavior expected of a double heterostructure junction laser operating in the vicinity of its lasing threshold. The analysis is based on a laser model in which the current-voltage characteristic of the p-n junction is determined by recombination alone. The first, second, and third current derivatives of the junction voltage are computed as a function of injection current for parameters thought to be typical of contemporary stripe-geometry lasers. The resulting derivative behavior exhibits a smooth transition from nonlasing to lasing emission qualitatively similar to that observed experimentally.