Font Size: a A A

Research On The Coupling-Excitation And Sensitivity Enhancement Of The Optical Microfluidic Sensor

Posted on:2013-09-24Degree:MasterType:Thesis
Country:ChinaCandidate:Q JiFull Text:PDF
GTID:2268330392469924Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
Opto-fluidic biosensor,based on WGM(whispering gallery mode), graduallybecome a hot research in the field of optical sensing due to its high sensitivity, highquality factor, small size and easy to integrate. Besides the above advantages, themicrotube simultaneously acts as the light guide channel and fluid transport channeldue to its unique structural feature, which simplifies the sensing system.So it has beengetting more and more attention. Based on Mie scattering theory, we establish bulkrefractive index sensing and surface refractive index sensing model.Then we derivethe multilayer microtubule WGM mode eigenequation and WGM mode fielddistribution of the microtubule. Then, we study the method to improve the sensitivityof the sensor by coating a high refractive index dielectric layer on the inner wall of themicrotubule. Finally, we distinguish the experimental spectrum. The major workcompleted as follows:Starting from the vector Helmholtz equation, we solve the electromagnetic fielddistribution of the microtubule and microsphere by using the separation of variablesmethod and construct vector function method, respectively. We establish the bulkrefractive index sensoring model and the surface refractive index sensing model. Andthen we derive the characteristic equation of the multilayer ring structure. Finally wemake a study on the influence of the resonance that the microtubule tilt or the externalenvironment temperature change by the resonance strengthen conditions.Based on the solve of the cylindrical coordinates vector Helmholtz equation, westudy the mode propagation in the tapered fiber and the matching of propagationconstants of the microtubule and the tapered fiber. Then, we derive the couplingcoefficient by making an approximate that the microtubule is equivalent to a straightwaveguide. We make a simulation to study the influence to the coupling coefficient ofthe waveguide width, curvature radius of the curved waveguide. Finally we calculatethe refractive index sensing sensitivity with different refractive indices and thicknessof the coating layer. An explanation from the geometrical optics is also made toexplain the phenomenon.We set up a prism-microtubule coupling system. Then make a study on thesensitivity of different whispering gallery mode by measuring resonance wavelength shifts corresponding to various concentrations of the Ethanol solution injected into themicotube. Finally, we distinguish the experimental spectrum.
Keywords/Search Tags:WGM, Biosensor, sensitivity, FDTD, microtubule
PDF Full Text Request
Related items