Chirped photonic crystal for spatially filtered optical feedback to a broad-area laser

We derive and analyze an efficient model for reinjection of spatially filtered optical feedback from an external resonator to a broad area, edge emitting semiconductor laser diode (DL). Spatial filtering is achieved by a chirped photonic crystal, with variable periodicity along the optical axis and negligible resonant backscattering. The optimal chirp is obtained from a genetic algorithm, which yields solutions that are robust against perturbations. Exemplary numerical simulations of the composite system with our optoelectronic solver indicate that spatially filtered reinjection can enhance lower-order transversal optical modes in the DL and, consequently, improve the spatial beam quality. (paper)