Fabrication And Temperature Sensitivity Of Polymer-Silica Compound Fiber

Evanescent wave has lots of advantages when used in fiber optic sensing, such as easy fabrication and high sensitivity. And polymers usually have high thermo-optic coefficient, and are easily tailored in molecular level and fabricated in macro-scale, so fiber optic components based on the interaction between polymers and the evanescent wave are easily fabricated and have extensive potential value. And the parameters of the propagating light in the fiber can be changed with temperature when the polymer is compounded with the optical fiber. They can be classified into two main categories: intensity-based and wavelength-encoded. Take it in consideration that silica fiber can be easily carried out in laboratory, here a single mode-multimode-single mode (SMS) fiber and a tapering fiber is, respectively, used as waveguide materials for composite fibers in this work. The polymer is compounded with the SMS fiber to study the temperature sensitivity of SMS fiber sensor by two main categories:the change of curvature of the fiber and the change of refractive index (RI) of polymer which is used as cladding of the SMS fiber. At the same time, a transform between leaky mode interference and guided one is obtained by changing temperature in the research work and the phenomenon around the transformation point is detaildly studied in the experiment. Temperature sensor was also made from the tapering fiber that was cladded with polymers. Fluoresence intensity can be measured by the tapering fiber without cladding, which has potential applications in medicine. Finally, temperature dependence of LSPR effect on photoisomerization of azobenzene units in Ag/poly (N-isopropylacrylamide)-block-poly{6-[4-(4-methylphenyl-azo)phenoxy] hexylacrylate}(short for PNIPAM-b-PAzoM) composite particles is studied, which results can be used in designing of new photo-responsive polymers. Main points of this work is detaildely shown as follows:All the details are shown as follows:1. A bent SMS fiber are fixed on a polymer whose volume will change with temperature. At the same time, the cladding of multimode fiber is etched by a chemical method, and substituted with a liquid material, which RI is higher than that of the core material of MMF. When the temperature is changed, the SMS transmission spectrum will change accordingly. It is found that when the curvature of bent MMF is changing along with the changing of temperature, the modes excited in the MMF will undergo significant changes and result in wavelength shift. 2. A novel model of SMS, which is fabricated using an elaborately designed polymer coating to replace the silica cladding of MMF, is proposed and experimented. The polymer is designed and synthesized for two characters:suitable RI and high thermo-optic coefficient. The transform between leaky mode interference and guided one is obtained and the phenomenon around the transformation point is observed in the experiment of polyurethane-SMS compound fiber.3. Polymer is synthesized and compounded with tapering fiber. Study the sensing property of compound fiber by detecting changes of intensity of fiber transmission at different temperatures. The tapering fiber also can be used to detect fluorescence intensity.4. A series of Ag/PNIPAM-b-PAzoM composite particles with varying concentrations of Ag nanoparticles are prepared by self-assembly. The distance between Ag nanoparticles and azobenzene units is determined by both of the concentration of Ag nanoparticles and temperature because hydrophiphilic PNIPAM chains are thermosensitive and adsorbed with Ag nanoparticles. Both trans-to-cis and cis-to-trans photoisomerizations of the composite particles are investigated at different temperatures and concentrations of Ag nanoparticles.