The structure of stripe‐geometry lasers is reported, in which a double heterostructure with a very thin active layer is fabricated on a substrate with two parallel ridges. It is shown that the structure is very much fitted for the high‐power, single‐mode oscillation. The maximum cw output obtained is approximately 100 mW/facet, which is the highest power output ever attained in fundamental transverse mode devices. The far‐field beam divergences parallel and perpendicular to the junction plane are as small as 6° and 16°, respectively.