A multimode interference splitter/combiner that includes a monolithic device for photonically coupling an input optical waveguide to first and second output optical waveguides. The input waveguide may be optically coupled to a first end of a MMI portion, while the first and second output waveguides may be optically coupled to a second end of the MMI portion. The input waveguide is coupled to a planar facet of the MMI portion so that the input waveguide may have a propagation axis that is oriented at an angle with respect to the planar facet of the MMI portion. A desired splitting ratio may be achieved by adjusting the angle between the input waveguide and the MMI portion.