Analysis of distributed-feedback diode lasers with gain-induced waveguiding

Coupled-wave formalism is developed to describe the coupling between modes that are guided by gain variation and by refractive-index discontinuities in two mutually perpendicular directions. The formalism is used to analyze distributed-feedback (DFB) stripe-geometry diode lasers, which are characterized by gain-induced lateral waveguiding. Analytical models for the gain distribution parallel to the junction plane are employed to evaluate the coupling coefficient, and results for various coupled-mode pairs and different gain profiles are presented and discussed. The effect of grating tilt is studied as well, and it is found that misaligned gratings may enhance the oscillation of DFB lasers in a single lateral mode.