Spectral Low-coherence Interferometry-based SPR using Telecommunication Wavelength

• Main Authors: Chi-Ting Tuan, 段奇廷
• Other Authors: Shih-Hsiang Hsu
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/10061990700945576441

碩士 === 國立臺灣科技大學 === 電子工程系 === 104 === 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 TE and TM polarized light was well controlled for the equal magnitude for SPR sensor injection, where only TM polarization will interact with the metal and dielectric layers to form the plasmon polariton. Then the linear polarizer was utilized to interfere the TE and TM polarizations to get the fringes on the optical spectrum analyzer (OSA). The use of TM based SPR effect would effectively generate the optical path difference from the TE polarization and demonstrate the spectral interferometry-based SPR. Compared with the spatial interferometry, the noise from the space increases for optical path will be eliminated by the wide-spectrum light source and OSA. Moreover, the real time and high dynamic fringes from the spectral interferometry-based SPR will be superior than the SPR wavelength interrogation by the laser scanning.