A selfaligned stepped substrate (S/sup 3/) AlGaInP visible laser diode structure is very attractive, because the laser structure, which includes a current blocking structure and an index guiding waveguide, is fabricated by only one-step MOVPE growth. The authors have improved the S/sup 3/ laser structure for high power operation, and modified the facet reflectivity and optical confinement factor to increase the power level at which catastrophic optical damage occurs. High-power operation at more than 70 mW has been achieved. The laser exhibits fundamental lateral mode oscillation up to 40 mW with an astigmatism of less than 1 mu m, and has stably operated at 50 degrees C for more than 1000 h under the condition with an output power of 20 mW.<<ETX>>