Reduction of AlGaAs Heterostructure High-Index-Contrast Ridge Waveguide Scattering Loss by Sidewall Smoothing Through Oxygen-Enhanced Wet Thermal Oxidation

We demonstrate the efficacy of oxidation smoothing of sidewall roughness in high-index-contrast AlGaAs heterostructure ridge waveguides via oxygen-enhanced nonselective wet thermal oxidation for reducing scattering loss. Single-mode waveguides of core widths between 1.5 and 2.2 ??m are fabricated using both the inward growth of a ~ 600-nm sidewall-smoothing native oxide outer cladding and, for comparison, encapsulation of an unoxidized etched ridge with a ~ 600-nm deposited silicon oxide cladding layer. On average, measured loss coefficients are reduced by a factor of 2 with the oxidation smoothing process.