A thermal oxidation fabrication technique is employed to form low-loss high-index-contrast silicon shallow-ridge waveguides in silicon-on-insulator (SOI) with maximally tight vertical confinement. Drop-port responses from weakly coupled ring resonators demonstrate propagation losses below 0.36 dB/cm for TE modes. This technique is also combined with "magic width" designs mitigating severe lateral radiation leakage for TM modes to achieve propagation loss values of 0.94 dB/cm. We discuss the fabrication process utilized to form these low-loss waveguides and implications for sensor devices in particular.

Quasi-TM-mode propagation loss of 1.83 dB/cm at lambda = 1.565 mum is achieved in horizontal Si(amorphous)-SiO2-Si(crystalline) slot waveguides with 8.3 nm slots fabricated on silicon-on-insulator. Waveguide loss is measured using a ring resonator with Q ~ 3x105.