Planar lightwave circuits, which include optical passive and active components, can be integrated with electronics to form planar lightwave integrated circuits (PLICs). Integration of PLICs onto standard electronic substrates (FR-4, Si) is an important step toward optical signal processing and signal distribution at the backplane, board, and chip level for sensing, interconnection, and other systems that utilize both optics and electronics. Further, if the topography of the entire planar optical system can mimic that of interconnection and integrated circuits, then the optics can be confined to the substrate plane, and the optical "circuits" begin to mimic electrical circuits in format. Additionally, beam turning out of the plane of the system is no longer mandatory. In this letter, the first demonstration of a planar lightwave interconnection consisting of a thin-film InP-based laser, waveguide, and thin-film InGaAs photodetector (PD) heterogeneously integrated onto a SiO2-Si substrate is reported. PD currents were measured as a function of laser bias current, and the laser to waveguide coupling efficiency was estimated at 22.6%. © 2005 IEEE.