Planar photonic crystal waveguides in silicon oxynitride

Most work on planar photonic crystals has been performed on structures based on semiconducting crystals such as Si and III-V compounds. Due to the high index contrast between the host material and the air holes (e.g., Si has n = 3.5), these structures exhibit a large photonic band gap. However, at visible wavelengths they absorb light very strongly. In contrary, silicon oxynitride (SiON) glasses offer high transparency down to blue and ultraviolet wavelengths. Thus, SiON photonic crystal waveguides can open for new possibilities, e.g., within sensing and life sciences. We have fabricated SiON glasses with different indices between 1.46 and 1.77 and we are currently fabricating photonic crystals in SiON on a silica buffer layer on Si. Simulations show that a complete band gap can indeed be created for TE-polarised light in the SiON structures, making them promising candidates for new photonic crystal waveguides and passive devices.