A new laser structure, the strip buried heterostructure (SBH) laser, using an active layer strip 2.5 to 10 &mgr;m in width, on a low‐loss waveguide is described. Typical test results with pulsed injection, for a 5‐&mgr;m strip width, show stable fundamental‐transverse‐mode operation linear light‐current characteristics up to 15 times threshold where the power output is 230 mW/mirror (without AR coating). Single‐longitudinal‐mode oscillation has also been observed up to twice threshold. Far‐field beam divergence of 8°–10° and 26°–30° was obtained in directions parallel and perpendicular to the junction plane, respectively.