Fabrication and characterization of compact silicon oxynitride waveguides on silicon chips

We investigate silicon oxynitride (SiON) waveguides for long optical delay lines on a silicon chip. With the choice of a moderately low refractive index contrast, a balance can be achieved between compact waveguide cross-section and low loss. The material composition and refractive index are characterized by Rutherford backscattering spectrometry and ellipsometry. High-temperature annealing is performed after waveguide fabrication so as to simultaneously remove light absorbing bonds in the materials and smooth the sidewall roughness at the core–cladding interface. A meter-long SiON waveguide is demonstrated on a centimeter scale chip.