The extended Rouard method is applied to the computation of a multi-absorbing-layer system for the optimization of surface plasmon resonance (SPR) sensors. Specifically, the effect of the properties of a metallic layer on the shape of the reflectivity and sensitivity curve is demonstrated in the case of a Kretschmann configuration. This theoretical investigation allows us to establish the best optical properties of the metal to obtain a localized SPR, given the illuminating beam properties. Toward the development of a sensitive biosensor based on SPR, we quantify the changes in reflectivity of such an optical biosensor induced by the deposition of a nanometric biochemical film as a function of the metal film characteristics and the illumination operating conditions. The sensitivity of the system emphasizes the potential of such biophotonic technology using metallic multilayer configurations, especially with envisioned metamaterials.
Surface plasmon resonance (SPR) sensing is an optical technique that allows real time detection of small changes in the physical properties, in particular in the refractive index, of a dielectric medium near a metal film surface. One way to increase the SPR signal shift is then to incorporate a substance possessing a strong dispersive refractive index in the range of the plasmon resonance band. In this paper, we investigate the impact of materials possessing a strong dispersive index integrated to the dielectric medium on the SPR reflectivity profile. We present theoretical results based on chromophore absorption spectra and on their associated refractive index obtained from the Lorentz approach and Kramers-Krönig equations. As predicted by the theory, the experimental results show an enhancement of the SPR response, maximized when the chromophore absorption band coincides with the plasmon resonant wavelength. This shows that chromophores labeling can provide a potential way for SPR response enhancement.
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