Abstract: An opto-electronic integrated circuit including an active ridge waveguide (60), for example, a semiconductor laser diode, and a passive buried heterostructure semiconductor waveguide (64). The two types of waveguides are chosen for their respective tasks so as to minimize the lasing wavelength dependencies arising from fabricational variations and to simultaneously reduce the allowable bending radius, thus reducing the chip size. The two waveguides are coupled by a transition structure (62) including a laterally undefined slab waveguide. A fabricational method is described that self-aligns the ridge and buried heterostructure waveguides so that the transition loss is negligible. The method can be integrated with the fabrication of a window facet (118', 118") between an end of the ridge waveguide and the chip edge, which prevents unintended back reflections from the chip edge.