Directional Coupler Biosensor Based on Thermooptic Detection Mechanism in Silica Waveguide

• Published in: IEEE photonics journal Vol. 8; no. 1; pp. 1 - 8
• Main Author: Tang, Tingting
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01.02.2016; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: biosensor; Biosensors; Couplings; directional coupler; Directional couplers; Refractive index; Silicon compounds; Sugar; thermo-optic effect; directional coupler; Biosensor; thermo-optic effect
• ISSN: 1943-0655; 1943-0655; 1943-0647
• DOI: 10.1109/JPHOT.2016.2520819

We propose a directional coupler (DC) biosensor to detect the concentration of glucose based on the thermooptic detection mechanism in silica waveguide. We discuss the design principles using the coupled-mode theory of DC and deduce the conditions for a valid biosensor model. The coupling length, the detectable refractive index range, and the sensing resolution for different silica widths and separation distances of the DC are presented by analytical calculation. By a tradeoff between coupling length and resolution of refractive index, we can obtain a sensor with a compact size of <inline-formula> <tex-math notation="LaTeX">48\ \mu\text{m}\times 30\ \mu\text{m}</tex-math></inline-formula>. The biosensor shows a resolution of about <inline-formula> <tex-math notation="LaTeX">1\times 10^{-6}</tex-math></inline-formula> for glucose concentration ranging from 1 to 200 mg/dL.