Fabrication and Application of Tapered Fiber Sensor with Nanometer Surface Roughness

• Main Authors: Yi-Hsin Tai, 戴義欣
• Other Authors: Pei-Kuen Wei
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/86083234689738623141

碩士 === 國立臺灣海洋大學 === 光電科學研究所 === 97 === In this thesis, optical fiber sensors using End-etching method were fabricated and tested. The fibers were coated with hot melt glue for chemical etching and used the capillary effect to form a sharp tip. As observed by the SEM, the tip size was around tens of nanometers and with a surface roughness also of nanometers. This kind of nano fiber tips was found to have very good sensitivity to environmental refractive index changes. The detection ability of the nano-fibers can achieve as high as 10-5 RIU (refractive index unit). In the experiment, fibers brought from four different commercial companies (3M, Thorlabs, AT&T and Prime) were tested. The single-mode fibers for 633nm and 1330nm wavelengths were compared by measuring the transmission intensity under various refractive index liquids. The results showed that 1330nm single-mode fibers had better sensitivity than 633nm single-mode fibers. The sensitivity is as high as 5870 %/RIU in the refractive index range rom 1.33 to 1.35. The detection limit is 10-5 RIU if the power stability of the light source is 0.2%. The Immunoglobulin G (IgG) proteins were detected for the demonstration of biosensing applications. In the experiments, 1 pg/ml IgG can be detected by using the proposed nano fiber probes The detection mechanism of the nano fiber sensors is based on light scattering by the rough surfaces of tapered fibers. A waveguide scattering model was used to account for the high-sensitivity and wavelength-dependent fiber sensors. When the refractive index difference between the tapered fiber and the surrounding medium increases, the transmission intensity decreases because of increasing light scattering. On the contrast, the transmission intensity increases when refractive index difference between fiber waveguide and outside surroundings is decreased. The proposed nano fiber sensors take advantages of small detection volume, high sensitivity, easy fabrication and very low cost.