Parabolic-confocal unstable-resonator semiconductor lasers-Modeling and experiments

Surface-emitting all-grating-based unstable-resonator lasers, suitable for integration with diffractive beam-forming elements, have been experimentally and theoretically studied. The lasers exhibit single spatial mode operation for a device width of 160 μm. The device performance is modeled using a beam propagation method, which accounts for spatial hole burning as well as thermal and carrier diffusion effects. Near- and far-field calculations are incorporated to facilitate the comparison with the experimental results. To achieve high-quality beam forming, it is essential that the wavefront of the guided optical mode is well defined and stable. Using the model, we study the dependence of the wavefront distortion on various parameters and show how these distortions affect the far-field characteristics. The results from the simulations agree well with the experimental work. We find that the laser performance is to a large extent controlled by thermal effects. At low-power operation, these effects can be compensated for, for a range of the injection current, by modifications of the resonator or outcoupler grating geometries