A Biochemical Sensor Based On Air-suspended-core Microstructured Fiber

The optical fiber sensing technology has broad range of applications in the industry of aerospace,railroad,bridge,petroleum etc.Microstructured fibers have been recently developed.Besides the applications in high power lasers and remote fiber optical communications,this type of fiber can also be used for biochemical sensing.The microstructured fiber has a number of advantages for sensing applications,such as low cost,compact device,and high sensitivity for detecting traceful chemicals.In this thesis,a novel microstructured fiber,i.e.,air suspended core?ASC?microstructured fiber was used.The properties of the fiber for evanescent field sensing were evaluated numerically first.Sensing performances of the fiber for detecting various biochemical substances were also studied experimentally.The content of this thesis includes:1.Firstly,a mathematical model was established for evaluating the evanescent field distribution of the ASC fiber when the micro-void was filled with different medium.2.The propagation loss of a 2?m-core ASC fiber was measured to be 0.16 dB/cm at 532 nm.The near-field and far-field guiding modes at 532 nm were also observed.Single mode operation can thus be confirmed in the fiber.The 2?m-core ASC fiber was filled with CdTe/CdS/ZnS Core/shell quantum dots solution as a fiber fluorescence spectroscopy.The detection limit was observed to be 5 nM and 1 nM respectively,when using forward and backward detection schemes.3.A series of chemical substances were further used for detection using the 2?m-core ASC fiber as a fiber Raman spectroscope.The Raman peak of water molecule at3438 cm^-1 was observed in pure water only with a low pump power of 125?W.The Raman peaks of acetone at 830 cm^-1,1730 cm^-1,2955 cm^-1 and the Raman peaks of methanol at 2870 cm^-1,and 2969 cm^-1 were detected,respectively.The concentration of the chemicals can be quantified according to the measured Raman peaks intensities.4.A 1?m-core ASC fiber was also used for biochemical sensing experiments.Firstly,the fiber was used for measuring the fluorescence spectrum of Rhodamine B and CdTe/CdS/ZnS Core/shell quantum dots solutions with different concentrations,using forward detection configuration.The limits for detecting these two substances were seen to be 50 nM and 1nM,respectively.In addition,Raman peaks of benzyl alcohol and glycol were observed with low pump power.In summary,the ASC fiber based biochemical sensor has many advantages including low cost,compactness,low pump power,high sensitivity,rapid response,and so on.Hence it indicates that the ASC fiber sensor is suitable for the detection of labeled biomolecules?protein,DNA,etc.?,microorganisms,and cancer cells etc.Furthermore,it is promising for monitoring the water pollution.