High-brightness single-mode double-tapered laser diodes with laterally coupled high-order surface grating

Double-tapered laser diodes with 23rd order laterally coupled surface gratings are fabricated at 913 nm. A narrow ridge waveguide restricts the lateral mode number, and tapered waveguides are utilized to enhance the output power. The gratings defined on the sides of ridge waveguide filter not only the longitudinal modes but also the high-order lateral modes. Experimentally, continuous wave power of over 560  mW/facet is achieved. The lateral far-field pattern exhibits a single-lobe profile and narrow divergence, and the lowest divergence angle is only twice the diffraction-limited one. The measured side-mode suppression ratio is about 27 dB. This device has great potential for high-power single-mode near-diffraction-limited laser emission with easy fabrication.