Research On The Coupled Plasmon-waveguide Resonance Sensing Based On The Back Focal Plane Imaging

Surface plasmon resonance sensors can can effectively realize real-time, non-destructive testing on biochemical reaction because of its advantages of high sensitivity and no need to label. Thus, it has great development potential in fields of environmental pollution, food safety, chemistry, and medical testing. In recent years, the rapid development of biological technology put forward higher requirements to detective methods of resolving power, specificity, universality and stability. Therefore, the coupled plasmon-waveguide resonance which has narrower half width and longer penetration depth of the reflectivity curve, has been focused due to its fundamentally improvement to the defects of traditional surface plasmon resonance.Traditional optical prism structure is widely used in the current academic circles for Bio-optical sensing system. The disadvantage of this structure is low spatial resolution which is far more than a single cell size. With the continuous progress of the scientific research, we will explore the microscopic field more extensively, so the research for measurement of refractive index and thickness of micro-structure is necessary. In this thesis, coupled plasmon-waveguide resonance sensing based on the back focal plane imaging system has been proposed, which can not only realize the real-time monitoring to refractive index and thickness of the local sample, but also substantially increase the spatial resolution of the measurement, it will be wildly used in chemical and biological fields.The main research works and conclusions are as following:l.We deduce the multi-layer film reflection theory formula and the expression of reflectivity curve of waveguide structure expression. And we use MATLAB to simulate the reflectivity curve of the coupled plasmon-waveguide resonance, to realize theoretical prediction of the reflection intensity and electric field intensity distribution in each layer. We use this method to find the optimal parameters of the waveguide structure, make depth of the reflectivity curve longer, so as to improve the measurement accuracy effectively.2.We built the Coupled Plasmon-Waveguide Resonance sensing based on the back focal plane imaging independently, the core part is an inverted oil-immersed objective lens and a 3D scanning platform, we use the white light source and filter group to achieve freedom switch of the wavelength of incident light. Various samples of waveguide structure has been designed and produced according to the calculation results. We evaporated silver film on the glass substrate at the thickness of 40nm, then spin photoresiston coated on the silver film at different thickness. The thickness of photoresist will determine whether the sample can effectively form the waveguide structure, so we have prepared a variety sample of different thickness of the polymer film.3.We observe and record the back focal plane imaging of coupled plasmon-waveguide resonance and conventional surface plasmon resonance, we transform the information of the focal plane imaging into corresponding coupling resonance angle by reading and calculating the pixels. The reflectivity curve can be fitted by MATLAB, so as to realize the measurement of unknown parameters. Through comparative analysis, we draw an objective conclusion:compared to the conventional surface plasmon resonance sensor, the coupled plasmon-waveguide resonance sensor has advantages of convenient calculation and accurate measurement. At the same time, we combine the radiation leak micro system based on back focal plane imaging principle and coupled plasmon-waveguide resonance sensor efficiently, making the spatial resolution of the measurement improved greatly.