Low-loss waveguides on silicon substrates for photonic circuits

Abstract

We have developed techniques for fabricating extremely low-loss channel waveguide structures on silicon substrates. We have made and evaluated waveguides consisting of combinations of Corning 7059 glass, phosphorus-doped silica glass (PSG), and boron-doped silica glass (BSG). The waveguides were fabricated on the surfaces of oxidized silicon wafers. The 7059 waveguides were patterned in rf-sputter-deposited films, and the PSG waveguides were made using atmospheric-pressure, chemical vapor deposition (APCVD), low-pressure, chemical vapor deposition (LPCVD), and plasma-enhanced, chemical vapor deposition (PECVD). BSG was used strictly as a cladding layer for many of the waveguides. We present a comparison of the waveguides prepared by these methods, and discuss the processing techniques used to make channel waveguides with propagation losses less than 0.01 dB/cm. The processes we used allowed us to make waveguides with cross-sections ranging from rectangular to nearly circular, and to build multiguide structures with the waveguides stacked vertically or arranged side by side. Applications for these waveguides include low-loss splitters and combiners, high-finesse resonators, switches, and wavelength division multiplexers/demultiplexers.