High optical power cw operation has been achieved at the wavelength range of 780 nm by newly developed window V‐channeled substrate inner stripe lasers. This laser consists of a waveguiding window region with a plane active layer and a stimulated region with a crescent active layer. These two regions are coupled to each other. cw optical power over 70 mW and low cw threshold current of 30 mA were obtained. Moreover, the fundamental transverse mode was observed up to 60 mW, and it was found that the beam waist along the junction existed at the mirror.