Threshold currents of double-heterostructure GaInAsP (1.38 μm) stripe lasers are typically a factor of two higher than those of a similar GaAlAs structure. A significant reduction in the threshold current, down to 4–5 mA per micrometre of active layer width, is obtained in a simple mesa structure having reduced interface recombination at the edges of the stripe. At a current of 100 mA, output power exceeds 5 mW, and up to 2 mW is butt-coupled into a multimode graded-index fibre (50 μm core, 0.23 NA).