Analysis of the dynamic response of multielement semiconductor lasers

A derivation of the dynamic response of a semiconductor laser consisting of more than one active element is presented. It is shown that the amplitude and phase of the modulated cavity adiabatically follows the complex resonance of the composite cavity; and using this relation, plus linearized carrier equations, the parameters characterizing the modulation response of the composite system are calculated. In the process, 'effective' differential gain constants and linewidth enhancement factors arise which take the place of the corresponding parameters in single-element lasers. In the case of a two-section laser, it is shown that frequency chirping under modulation is present except under special conditions; those conditions are identified and it is shown how chirping can be avoided.