Experimental Demonstration of Deeply-Etched SiO $_{2}$ Ridge Optical Waveguides and Devices

Deeply-etched SiO₂ optical ridge waveguides are fabricated and characterized. A detailed discussion of the fabrication process (especially for the deep etching process) is presented. The measured propagation losses for the fabricated waveguides with different core widths range from 0.33 ~ 0.81 dB/mm. The loss is mainly caused by the scattering due to the sidewall roughness. The losses in bending sections are also characterized, which show the possibility of realizing a small bending radius (several tens of microns). 1 × N (N = 2, 4, 8) multimode interference couplers based on the deeply-etched SiO₂ ridge waveguide are also fabricated and show fairly good performances.