Surface plasmon resonance spectrometer in the double prism configuration: Fast characterization of the thickness and dielectric constant dispersion of thin films

Surface plasmon resonance (SPR)-based sensors are widely used to measure thin film thickness, material dielectric constants, biomolecular interactions, and more. However, conventional monochromatic setups limit the simultaneous determination of dielectric constant dispersion and film thickness. To address this, we developed a fully automated wavelength-resolved SPR using a double-prism Kretschmann configuration. Combining this setup with a computational approach based on Fresnel equations and the Nelder-Mead optimization method, we introduced a novel technique to simultaneously determine the dispersion (520-1000 nm) of the real and imaginary components of the dielectric constant of thin films directly from SPR curves. As far as we know, this is the first time an SPR spectrometer has accomplished such a remarkable achievement. As a proof of concept for biosensor applications, we determined the thickness and dielectric constant dispersion of gold and bovine serum albumin thin film. These thicknesses were validated through atomic force microscopy, and the dielectric constants aligned closely with literature values obtained by ellipsometry. The developed SPR system enables precise measurements of these parameters within a short time (10 minutes), paving the way for future applications in advanced sensors and biosensors.