Golden layer characterization using a phase shift induced by surface plasmon resonance

Abstract

In sensing applications utilizing the effect of surface plasmon resonance (SPR), a thin film of gold is widely used as the plasmonic layer. Despite advantages of gold over other metals, characterization of its optical properties is not sufficient as is evident from the measured responses at different angles of incidence. In this paper, a new method of determining the optical constants of a thin golden layer is presented. The method is based on measuring the phase shift between p- and s- polarized optical waves induced by SPR for air in the Kretschmann configuration with an SF10 glass prism and an SPR structure. The SPR structure comprises a gold coated SF10 slide with a chromium adhesion layer. In addition, a birefringent crystal is included in the setup to attain the spectral interference. Information about the phase shift induced by SPR is inscribed in the spectral interferogram recorded by a spectrometer and can be retrieved using the Fourier transform analysis. The measurements are performed for different angles of incidence to obtain the spectral dependence of the optical constants of the golden layer. Measured data are fitted to a model and in addition, the feasibility of the method is demonstrated in measuring the phase response for distilled water.