Low loss Si_3N_4–SiO_2 optical waveguides on Si

Abstract

We have developed an optical integrated circuit waveguide technology based on conventional Si processing. We demonstrate waveguide losses of μm wavelength range. We use a high refractive-index core of Si₃N₄ surrounded by SiO₂ cladding layers, which provides a highly confined optical mode adequate for butt coupling to channel substrate buried heterostructure lasers. We report the first IR transmission experiments in these waveguides and find two absorption peaks associated with H in SiO₂ and Si₃N₄ layers at 1.40 and 1.52 μm, respectively. The peak absorptions are 2.2 and 1.2 dB/cm, respectively, and these peaks can be largely removed by annealing at 1100–1200°C.