Spectral and Angular Responses of Surface Plasmon Resonance Based on the Kretschmann Prism Configuration

摘要

The present study investigates the optical characteristics and the spectral and angular responses of a Kretschmann surface plasmon resonance (SPR) sensor configuration that is widely used in biological and chemical sensing applications. In order to examine the influence of wave interference and optical properties of thin films on angular variation of reflectance at different incident angles, the Kretschmann SPR configurations made of gold films with 30, 52, and 70 nm thicknesses were fabricated and the reflectance was detected using a 633 nm He-Ne laser, θ-2θ rotation stages, and a silicon pin photo-detector. In particular, this study involved the numerical analysis of angular and spectral variation of reflectance estimated using the characteristic transmission matrix (CTM) method. It was found that the SPR sensitivity became highly dependent on the gold film thickness, indicating that in the thinner gold film case, the reflectance was recovered slowly after the SPR angle, whereas as the gold film thickness increased, the magnitude difference between the maximum and the minimum reflectance measured near the SPR angle was smaller than in other cases. From the numerical analysis, it was shown that the phase shift is the most sensitive physical parameter for SPR sensor by comparing estimated FWHM values of reflectance, phase shift, and enhancement of magnetic field intensity. Therefore, it was concluded that an appropriate metal thickness of around 50 nm was found for higher sensitivity.