In addition, this project also investigated schemes that might enhance the phase change in the SPR sensor. The "double-pass" and "multi-pass" approaches through which the SPR phase can be amplified upon hitting the sensor surface more than once, have been experimentally studied and successfully demonstrated. A double-pass method can immediately offer two times of phase change as compared to the singlepass one. Accordingly the multi-pass scheme offers a higher then two times phase enhancement. Such improvement in phase detection is extremely important for biosensing applications involving small molecules, small proteins, DNA and etc. Another approach for detection performance improvement is to incorporate a multilayer configuration for the biosensing surface. In order to improve the dynamic measurement response, we proposed to use a multiple resonant angle measurement approach in conjunction with the single-beam self-referenced phase-sensitive SPR configuration. With the use of many multiple incident angles, the system provided sensing capability that covers a refractive index (RI) 1.33 to over 1.38. A 128-element array detector was employed to measure the resonance phase change over the range of the incident angles to ensure a reasonably continuous phase response curves achievable from the system. / This project is concerned with the development and optimization of optical sensors based on measuring the phase change of surface plasmon resonance (SPR) effect. The phase sensitive SPR technique provides very high sensitivity performance due to the fact that an abrupt phase jump occurs near the resonance dip, thus resulting in large phase shift with very small change in the sensing medium. A range of different measurement techniques for enhancing system sensitivity have been investigated. Moreover we also studied the phase change characteristics around the SPR dip region by means of simulation in order to explore various approaches for achieving further improvement in sensitivity and as well as wide dynamic range. Since SPR is caused by electron charge density oscillations in metal surface in which the wave momentum required for plasmon wave excitation is always larger than that for free space, an inverted prism-coupling scheme (prism-metal-dielectric) is commonly used and this configuration was also employed in our experimental setup, particularly for the SPR biosensor based on differential phase Mach-Zehnder interferometer configuration. This design primarily operates by taking advantage of the fact that SPR only affects the p-polarization while leaving the s-polarization unchanged. This means that differential phase measurement between the p- and s- polarizations will result in SPR signals that are completely free from any disturbances that are common to both channels. Experimental results obtained from glycerin/water mixtures indicate that the sensitivity limit of our scheme is 5.48 x 10 -8 refractive index unit per 0.01° phase change. To our knowledge, this is a significant improvement over previously obtained results when gold is used as the sensor surface. While acknowledging that accurate optical alignment is a crucial requirement for the Mach-Zehnder interferometer and it is often not easy to maintain high degree alignment accuracies in practical situations, we have developed a versatile and low cost single-beam self-referenced phase-sensitive surface SPR sensing system. The system exhibits a root-mean-square phase fluctuation of +/-0.0028° over a period of 45 minutes, i.e. a resolution of +/-5.2x10 -9 refractive index units. The enhanced performance has been achieved through the incorporation of three design elements: (i) a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected; (ii) a differential measurement scheme to eliminate spurious signals not related to the sensor response; (iii) elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulator. Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional florescence-based techniques. / Wu, Shu Yuen. / Source: Dissertation Abstracts International, Volume: 73-06, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 132-147). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_344822 |
| Date | January 2011 |
| Contributors | Wu, Shu Yuen., Chinese University of Hong Kong Graduate School. Division of Electronic Engineering. |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, theses |
| Format | electronic resource, microform, microfiche, 1 online resource (xxi, 147, [5] leaves : ill. (some col.)) |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
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