| Summary: | 碩士 === 國立臺灣大學 === 應用力學研究所 === 96 === Waveguide interferometer is a sensor based on the characteristics of total internal reflection (TIRF). When a light beam propagates in a waveguide structure, the evanescent wave accompanies TIRF is very sensitive and can be used to sense the changes of the properties on the boundary. Therefore, we can combine the waveguide structure and interferometry together so as to utilize some appropriate algorithms to detect the phase change of different sample solutions. The information of phase change can then be applied to calculate the refractive index and thickness variations of the boundary. As a result, the waveguide interferometer is suitable for being a biosensor.
The main purpose of this thesis is to pursue a preliminary research of a fiber-based waveguide interferometer, which I chose the polarization maintaining fiber to built the guide tunnels. Upon the design of the fiber chip, a double layer Teflon fiber fixture is fabricated by machining. In addition, the design can solve the problem of defining light polarizations while the light beam propagating through the sensing window. In order to accomplish the function of dual-polarization detection, I used the polarizer and the polarization controller to switch the light polarizations of reference beam and sample beam. The construction of Young’s interferometry is chose to be the optical path for phase analysis. Utilizing the CCD camera to catch the interference fringes and then rotated the analyzer to obtain five images. At last I used five step phase shifting method to get the phase distribution diagram.
The system has proved its stability and reproducibility by DI water and 10X PBS solution. In order to make sure the fiber-based waveguide interferometer has the ability to recognize between the sample solutions with different concentrations, I used two light polarizations (which were orthogonal to each other) of the sample beam to detect the PBS solutions. By the results we knew that the system would have different phase changes with respect to measure the specimen which have individual refractive index themselves. In summary, the system has been proved that it has the fundamental ability to distinguish the sample solutions with different concentrations.
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