%0 Journal Article
%T Detecting Phase Shifts in Surface Plasmon Resonance: A Review
%A Y. H. Huang
%A H. P. Ho
%A S. Y. Wu
%A S. K. Kong
%J Advances in Optical Technologies
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/471957
%X Under certain conditions, a surface plasmon wave along a metal-dielectric interface can be excited by an optical beam. The reflected optical beam will then undergo changes in both intensity and phase. As the level of intensity or phase change is quite sensitive to the coupling conditions such as the molecule concentration on the metal surface, this phenomenon has been utilized for label-free detection of biological species and characterization of molecular interactions during the last two decades. Currently, most of the commercial surface plasmon resonance (SPR) sensors rely on the detection of absorption dip in angular or wavelength spectrum. However, recent researches have shown that phase detection has the potential to achieve lower limit of detection (LoD) and higher throughput. This paper, thus, intends to review various schemes and configurations for SPR phase detection. The performance advantages and disadvantages of various schemes will be emphasized. It is hoped that this paper will provide some insights to researchers interested in SPR sensing and help them to develop SPR sensors with better sensitivity and higher throughput. 1. Introduction Surface plasmons are guided electron oscillations confined to a thin layer of the interface between two materials with negative and positive real parts of permittivity (e.g., a metal-dielectric interface). Surface plasmons can be excited by photons when the optical wave vector parallel to the interface matches the propagation constant of surface plasmon. Under optimal conditions, optically excited surface plasmon resonance (SPR) could be quite strong and a large portion of optical energy is dissipated into a guided electromagnetic wave along the interface. As the extent of energy transfer is ultrasensitive to the coupling conditions, parameter such as the refractive index of dielectric layer can be accurately determined by monitoring the reflected light intensity or phase. This serves as the basis for various SPR sensors. The first observation of surface plasmons is reported by Wood [1] when he used metallic grating to study the diffraction of polychromatic light and found an unexpected narrow dark band in the spectrum. The first theoretical investigation of surface electromagnetic waves was carried out by Zenneck [2] a few years later. Experimental researches on SPR, however, only started when Otto [3] and Kretschmann and Raether [4] demonstrated optical excitations of surface plasmons using different configurations of attenuated total reflection (ATR) method. These pioneering works had formed the
%U http://www.hindawi.com/journals/aot/2012/471957/