Research On Fluorescence Far-field Directional Luminescence Enhancement And Micro Displacement Sensing Based On Microcavity Structure

The rapid advancement of science and technology since the second half of the twentieth century has brought people's understanding of life gradually from the organ and tissue levels to the cellular and molecular levels.Biosensing has become the frontier field of contemporary scientific research.Biosensors are widely used in environmental monitoring,food engineering,clinical medicine diagnosis and other fields.Improving the sensitivity of biosensors is of great significance to the development of life sciences.Fluorescence detection,as a commonly used detection method in the field of biosensing,has the characteristics of real-time,high efficiency,intuitiveness,and sensitivity.Quantum dots are widely used as fluorescent probes in fluorescence detection due to their advantages such as high fluorescence intensity,good optical stability and good biocompatibility compared with other fluorescent dyes.Therefore,improving the sensitivity of quantum dot sensing is crucial to the development of the field of biosensing.Firstly,a metal channel-dielectric microcylinder composite microcavity structure is proposed,which enhances the far-field directional emission of quantum dots.First,the effects of quantum dot polarization and different structures on the directional emission effect of fluorescence were studied.Then,the relationship between the directional emission intensity of quantum dots in the composite microcavity structure and the radius and refractive index of the dielectric microcylinder was studied.The effects of changes in the position of quantum dots in the microfluidic channel and the amount of solution on the fluorescence enhancement effect were studied.When the metal channel is 4 microns wide,the height is 10 microns,the dielectric microcylindrical radius is 5 microns and the refractive index is 1.5,compared with the glass structure,the fluorescence enhancement multiples of quantum dots in the near field and far field of the structure are as high as 89.88 and 31.75 times respectively.The mechanism of enhanced fluorescence directional emission under the combined effects of scattering,constructive interference,resonance mode,photon nanojetting and lens effect is described for the composite structure of metal channel-dielectric microcylinder microcavity.Finally,the effect of the composite microcavity structure on the excitation of quantum dots is studied,indicating that the structure can efficiently excite the quantum dotsSecondly,the structure of nanofluidic channel-ring resonator is proposed to realize quantum dot micro-displacement sensing.The relationship between the coupling effect of the fluorescence emitted by quantum dots between the structures and the polarization state of the quantum dots,the nanofluidic channel-resonant cavity spacing,the size of the resonant cavity,and the width of the nanofluidic channel are studied.It was found that when the quantum dots are z-polarized,the distance between the nanofluidic channel and the lower waveguide and the resonator is 200 nm and 250 nm,the outer and inner diameters of the resonator are 2.3 microns and 2.1 microns,and the width and wall thickness of the resonator are 100 and 50 nanometers respectively,The fluorescence emitted by quantum dots is well coupled with the structure.Quantum dot micro-displacement detection is realized based on the above parameters.Then,the relationship between the sensitivity of quantum dot microdisplacement detection and the refractive index of the structure,the spacing between the nanofluidic channel and the resonant cavity is studied and clarified,which provides ideas for improving the sensitivity of the sensing and selecting the structural material.