A monolithic integration between an active and an external passive waveguide in such a way they are directly butt‐jointed in a single epitaxial step is demonstrated in the InP system. The growth behavior during nonplanar metalorganic vapor‐phase epitaxy on a patterned InP substrate was investigated by using a periodic structure on GaInAs or InGaAsP/InP layers. A 1.5‐mm‐long ridge laser consisting of an active guide butt‐jointed to a transparent waveguide has exhibited lasing oscillation at 1.5 &mgr;m with a threshold current of 82 mA. A coupling coefficient of 60% has been experimentally measured.