Ultra-low loss Si_3N_4 waveguides with low nonlinearity and high power handling capability

We investigate the nonlinearity of ultra-low loss Si₃N₄-core and SiO₂-cladding rectangular waveguides. The nonlinearity is modeled using Maxwell’s wave equation with a small amount of refractive index perturbation. Effective n₂ is used to describe the third-order nonlinearity, which is linearly proportional to the optical intensity. The effective n₂ measured using continuous-wave self-phase modulation shows agreement with the theoretical calculation. The waveguide with 2.8-μm wide and 80-nm thick Si₃N₄ core has low loss and high power handling capability, with an effective n₂ of about $9\times {10}^{-16}$cm²/W.