Breath sensing is an effective tool for health monitoring. Previously, high-mesa waveguide structures have been proposed by our group for realizing a compact breath-sensing photonic circuit. By using the doped SiO2 as the waveguide core, 50% concentration CO2 has been detected. One issue of preventing parts per million (ppm)-order detection is the low portion of evanescent light (Γair = 2.2%) in the doped SiO2 waveguides. In order to realize low propagation loss α and high Γair simultaneously, thin silicon (Si) waveguides with a Γair as high as 37.6% have been proposed and fabricated in this work. A thermal oxidation technique was applied to further reduce α, so that α was decreased from 1.45 to 0.84 and 0.29 to 0.2 dB/cm for the 0.5 and 3-μm-wide waveguide, respectively. According to our analysis, the significantly decreased α is attributed to recovering the damaged Si core and smoothing the waveguide sidewalls. The high Γair and effective loss reduction showa promising potential of applying Si high-mesa waveguides to realize ppm-order sensing.
All Science Journal Classification (ASJC) codes
- Atomic and Molecular Physics, and Optics
- Engineering (miscellaneous)
- Electrical and Electronic Engineering