| In this thesis,kinds of novel fiber-optic chemo- and bio- sensors based on mode-filtered light detection (MFLD) were presented,originating from the proposition of MFLD mechanism. The term of mode-filtered light refers to the observation that light initially propagating down an optical fiber can be decoupled from that fiber by increasing the cladding RI at the core/clad interface with a permeating analyte,thus changing the allowable propagating modes within the fiber,resulting in a continuous and nearly linear increase in mode-filtered light with increasing cladding RI. So,MFLD provides a new way to obtain optical information for optical chemo- and biosensors. Compared with conventional detection methods,in which the detector was placed at the distal end of the fiber,MFLD has advantages in much higher singnal-to:noise (S/N) ratio and sensitivity,since the analyte signal is measured against a much lower background by placing the detector at the fiber-optic profile instead of the distal end.The contents of the thesis include two parts. In the first part,the work has been done toward the development and fabrication of the instruments,and discussion about the signal sensing theories based on the fiber-optic mode-filtered light detection.1. Develop and fabricate the mode-filtered light sensing instruments. This part of work involves several key problems as follows:-1) Coupling technology of laser source with the optical fiber;2) The construction of the sampling device and the selection of relevant parameters;3) The technical platform for the treatment and modification of fiber/capillary annular column sensing element;4) The selection of the size or parameters,design,machining and assembly of the sensing instruments;5) The construction of the multichannel detection system,the collection and processing of the digital signals and the exploiture of relevant software;And so on.According to our design,we constructed an uncoated fiber-optic mode-filteredlight sensing instrument based on general and fast detection and a modified fiber-optic mode-filtered light sensing instrument with synchronization of selective response to mixed components. Due to the novelty of this research work,two of mode-filtered light sensing instruments assembled by our lab were purchased by Hong Kong Baptist University for cooperative research. On the basis of this,we further developed a novel fiber-optic mode-filtered light equipment for capillary electrophoresis,and obtained a patent.2. Derived from optical waveguide fundamentals,outstanding advantages of MFLD in high S/N ratio and sensitivity were theoretically presented. To resolve inconsistent change tendencies of mode-filtered light obtained in bare core sensing system and in modified sensing system,that is,the mode-filtered light signal declines with the increase in analyte RIs in bare core sensing system but increases with the increase in analyte RIs in modified sensing system,we started with light energy radiation theory,and obtained the details of MFLD mechanism by discussing in detail the radiant energy's reflection and refraction at the interface,thus establishing a mathematical model of MFLD. We concluded that the inconsistent change tendencies of mode-filtered light were essentially coherent.In modified fiber-optic sensing system,quantitative analysis of the interaction of the analytes with the cladding is the theoretical foundation of fiber-optic mode-filtered light chemo- and bio- sensing. In our study,we took example for the fused silica fiber that we used,to deduce a mathematical expression for MFLD. We derived an expression that related the mode-filtered light signal as a function of the capacity factor of the analyte,RI of the analyte,injected volume and concentration of the analyte and the mobile phase linear flow velocity. Inspection of this equation reveals that detector sensitivity for a given configuration is primarily determined by two terms. One term predicts increasing sensitivity with increasing difference between the RIs of...
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