High‐power and high‐reliable operation of transverse‐mode stabilized InGaAlP laser diodes has been achieved by a selectively buried ridge waveguide structure with a thin (0.02 &mgr;m) active layer. A composition‐shifted In0.5+&dgr;Ga0.5−&dgr;P active layer was employed in order to improve the temperature characteristic. A maximum cw light output power of 54 mW was obtained for the laser with antireflection and high‐reflection coatings. A high‐power cw operation above 30 mW output power was maintained even at a 60 °C heat‐sink temperature. Stable cw operation exceeding 1000 h has been achieved for 20 mW output power at 50 °C.