Scattering in low-loss GaAs/AlGaAs rib waveguides

Abstract

Single-mode rib waveguides with low propagation loss (0.2 dB/cm) were fabricated on GaAs/AlGaAs single heterostructures by dry etching. The attenuation of these guides was measured to study the effect of rib structure on propagation loss at 1.52 μm. An increase in loss with increased rib height and decreased rib width was associated with scattering due to a rib surface roughness of approximately 50 nm for ion milled waveguides. Fabrication with reactive ion etching reduced the rib roughness and its associated scattering loss by a factor of 3 or more in waveguides with strong optical confinement (effective index difference of 0.012) of the fundamental guided mode.