Refractive index sensor utilizing thermo-optic effect of silicon waveguide

We propose a refractive index sensor based on thermo-optic (TO) effect in directional coupler (DC) with silicon waveguide to detect physiological concentrations of glucose in water. A temperature compensation method is used to realize a refractive index sensor with high sensitivity. The coupling length of the DC with silicon waveguide is calculated by coupled-mode theory. Different silicon width and separation distance of DC have great influence on the sensitivity and resolution to refractive index change of glucose water. Based on simulation results, a sensor with a size of 119.5 μm × 10 μm can be obtained with a resolution of about 1.49 × 10−6 and a sensitivity of 867 K/RIU for glucose concentration less than 1000 mg/dL using highly sensitive detectors with a noise equivalent power (NEP) of picowatt. We also give the equivalent circuit for the refractive index sensor in order to realized opto-electronic integration.