Studies On Sensitive Label-Free Biodetection Based On Microfiber Coupler

Optic fiber biosensor is advantageous in many aspects,such as easy to fabricate,easy to use,small size,high sensitivity,and anti-electromagnetic interference.After years of research,fiber biosensor has progressed greatly in bio-detection,light transmission theory and manufacturing technique.However,in order to obtain a high sensitivity,the tapered fiber has to be manufactured to nanometer level,this will cause difficulties in manufacturing,sensor packaging,and transportation.Moreover,although the nano-fiber has high detection sensitivity,non-immune adsorption to the fiber will appear when detecting in complex sample,which reduces its repeatability.To solve these problems,In this thesis,focusing on micro fiber coupler,we studied to obtain high manufacturability,high sensitivity of new type of optical fiber sensing method and improved the surface modification methods of bio-detection specificity.The preparation technology of micro fiber coupler and the verification of physical and bio-detection characteristics were carried out.The main contents of this thesis are as follows:1)Based on the waveguide coupling mode theory,we studied the transmission characteristics and mode characteristics of the micro-fiber coupler.The coupled-mode equations of the 2×2 micro-fiber coupler for two identical fibers are introduced.The model is verified by the RI detection experiment.2)We studied the fabrication method of nano-fiber,and the method to obtain high surface finish quality and high uniformity and consistency of micro fiber coupler by melt drawing technique is given.3)Detection sensitivity,detection limit and specificity of the micro-fiber coupler had been experimentally studied.The experimental results show that the sensitivity and specificity of biosensor can be improved by monitoring the real-time process of the sensor's dynamic process.The sensor can distinctively identify the biomolecule-specific binding and non-specific binding,which ensures the credibility of immune detection.At last,its reusability was studied;it shows that the micro-fiber optic coupler can be reused for more than 10 times.