Research On Optofluidic Biosensor Based On Microcapillary

Opto-fluidic biosensor based on microcapillary, with its unique resonant whispering gallery mode (WGM), which allows high sensing sensitivity, realizes the label-free detection of biological reagents. Also, due to the small size and easy to integrate, this biosensor has very important research value and application prospects. The main point of this paper is to establish a theoretical model of the optic micro fluid biosensor, and to build an experiment system in order to implement the micro fluid sensing detection, combined with the model. The analysis method is that, first, theoretically derivate the relevant parameters of the micro-ring sensing model, then numerically simulate the micro-ring sensor based on the well-known finite-difference time-domain(FDTD) algorithm, finally set up the experiment system to achieve the micro-ring biosensor and analyze the results using the theoretical calculation. The major works completed are as follows:Based on the coupling mode theory and the FDTD method, the property of the coupling between the straight waveguide and the micro-ring is thoroughly investigated, the theoretical model of the micro-ring resonators are established, and at last get the performance parameters of the micro-ring structure , such as resonant wavelength, free spectral range, quality factor and peak width at half, etc. We deduce the distribution of the electromagnetic field equations under the cylindrical coordinate from Maxwell's equations, and according to the radial electric field profile, we get the required relationship between the corresponding structure parameters. Enhanced notch depth is demonstrated in micro-ring resonator which is generated either by the nanometer-scaled gratings along the ring sidewalls or by evanescent directional coupling between two concentric rings.Based on the FDTD algorithm, using the FULLWAVE simulation engine which is a part of the RSoft Photonic Suite simulates the theoretical models of the micro-ring resonators. The relationship between parameters, radial and circumferential electric field pattern observed by simulating. Grating-assisted and concentric micro-ring resonators with different parameters are simulated.Microcapillary biosensor was established with a prism and a microcapillary. With the prism made from ZF13 material, WGM of the microcapillary is successfully observed by evanescent coupling. The mixture of water and ethanol were used for experiment research on refractive index change sensitivity of microcapillary biosensor. Sensitivity of the biosensor observed in different incident angles.