Enhancement of lateral mode discrimination in broad-area VCSELs using curved Bragg mirrors

This paper studies a novel technique for enhancing the single mode properties of large-area oxide-confined vertical cavity surface emitting lasers (VCSELs). It utilizes a nonplanar shadow masked epitaxial growth to spatially detune part of the upper Bragg stack from the lower stack. The resulting mirror reflectivity modulation is used to enhance the discrimination between the lateral modes. Compared to other techniques, this method results in a larger difference in threshold gain between the lateral modes. We have developed a quasi-three-dimensional (3-D) optical model to analyze this laser. Simulation results indicate that even a small curvature can enhance the mode discrimination, and single mode operation may be possible for VCSEL diameters much greater than 2 μm.