Surface plasmon enhanced differential reflectance technique for ultra-thin film monitoring

Surface plasmon enhanced differential reflectance (DR) technique has been theoretically investigated in this paper. A plasmonic gold grating substrate is proposed to greatly enhance the sensitivity of the DR technique. The results show that the sensitivity of the technique can be enhanced by at least one order of magnitude compared to that with SiO₂ substrate (dielectric substrate) and the enhancement effect is most significant for ultra-thin films with thickness of less than 1 nm. It is further demonstrated that the technique can be also used for detecting the refractive index change of thin films with a much enhanced sensitivity.