表面プラズモン共鳴の理論 チュートリアル

Abstract

In the surface plasmon resonance (SPR) measurement we can detect the change of the film thickness (refractive index change) in the sub-nonometer scale using a low-cost home-made appratus (He-Ne laser, rotating stage, photo-diode detector, prism, maching oil, and 50 nm gold film on a glass plate, See Appendix). In this sense SPR is widely used, in particular, as the immunoassay to detect label-free antigen-antibody reaction. When light is irradiated to the optical prism |thin metallic film (usually 50 nm gold film is used)| sample system, the reflectivity of the light becomes almost zero at the angle of incidence where the surface plasma wave of gold surface can couple to the part of the incident light. 1 This angle is called SPR angle and is very sensitive to the film thickness (refractivity) of the sample. In the usual automated SPR measurementanalysis routine one can get the SPR angle shift and the the change of the film thickness (and/or refractivity), thereby the measurement may be one of the ”black-box”. However I think it is important to know the principle for the people to do something new by an detailed analysis of the measurements. From the name ”plasmon” one may misunderstand that the quantum mechanical understanding is required for SPR principles, but the phenomena can be understood from the classical optics (or electromagnetic theory) which explain the light reflection, transmission, and absorption for the multi-layer medium. In the famous book by Raether the principle of SPR was written completely, but at least for me it is not easy to understand because the book may be for specialist. 2 This note is written for my self-study of SPR principle in order to analyze the SPR curves, 3 . ,later was publish in ”Review of Polarography, 48, No3. 2002, 209 ”, and posted the revised version at http://www.scl.kyoto-u.ac.jp/ masahiro/sprtheory.html. (I am very happy that many people give me contacts and some comments.) In this note on SPR theory I also describe the basics of the light reflection, transmission, absorption at the surface of dielectrics or metal, then it is my pleasure that