Biosensing Study of Waveguide-Coupled Surface Plasmon Resonance

• Main Authors: Zhi-Hao Jian, 簡志浩
• Other Authors: Shih-Hsiang Hsu
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/55918081968839033846

碩士 === 國立臺灣科技大學 === 電子工程系 === 103 === Surface plasmon resonance (SPR) is a physical phenomenon that happens between the interface of metal and non-conductive materials and can be induced by external electrons or photons injection. When the light wave is propagating from the high to low refractive index in the material and the incident angle is larger than the total internal reflection, the free electrons in the metal will be excited and resonate in the longitudinal direction at the specific angle. The attenuated total reflection is typically utilized to generate the non-radiative surface plasmon wave. We can say that the incident light angle is large than the total internal reflection, the evanescent wave in the transmitted medium will penetrate into half of the wavelength. When the propagation constants between the evanescent and surface plasmon waves are the same, the surface plasmon resonance is happening and the reflective light will rapidly drop to the minimum. By applying this feature onto the biosensing applications, the real-time, high sensitivity and label-free detection are possessed. Therefore, it has been extensively utilized in bio-detection and immunochemistry for its efficiency in analyzing the small refraction index variation of detected materials. Typically there are two modulations, angle and wavelength, for surface plasma resonance, which were sensing the analytes using the smallest reflection at the resonance angle and wavelength. In this thesis, the 1550-nm wavelength for fiber optic communications, used as the light source, was injected on the prism interface to generate the surface plasmon between the metal and non-metal materials. The SPR wavelength modulation was implemented by the fiber-optic communication wavelengths due to its deep penetration depth and high sensitivity compared with the visible light. In this thesis the biosensor will only explore the prism coupling with the wavelength modulation for characterize the surface plasmon resonance. In order to sense the small amount of analytes, such as short base pair synthetic miR-21 DNA, the waveguide coupled surface plasmon resonance demonstrated more sensitivity than the traditional one because of its additional guided wave and metal layers to enhance the evanescent wave between the layers of metal and guide wave for narrow reflective spectrum. After the simulation from the commercial software Matlab, the full width at half maximum from the waveguide coupled surface plasmon resonance is 2.11 times than the tradition one. The system resolution is also improved up to 2.13 times for better sensitivity in biosensing. Our experimental data showed that the thickness of metal directly on the prism would significantly affect the linewidth. On the other hand, the wavelength modulation sensitivity on the waveguide coupled surface plasmon resonance is less sensitive to injected angle variation compared with the traditional one.