Optical Index Prism Sensitivity of Surface Plasmon Resonance Imaging in Gas Phase: Experiment versus Theory

Recent advances in SPR imaging detection in the gas phase have led to the development of an optoelectronic nose (opto-eN) requiring the need for optical sensitivity characterization of such devices. Understanding the optical contributions will have an implicit relevance to sensitivity enhancement of SPR imaging in the gas phase valuable to improving the performance of opto-eN and potentially opening new applications as gas sensors. In this paper, we analyzed the optical contributions to the sensitivity of the SPR imaging prisms and potential insights into their contributing factors. We established a characterization method for the SPR prism sensitivity that is independent of the carrier gas considered. Then, by using this sensitivity parameter, the influence of two different kinds of adhesive layers, Cr and Ti, of the gold coated-prisms was studied. Furthermore, we considered a theoretical model to rationalize our experimental results, which demonstrated the relevance of surface topography to the optical index sensitivity. Those surface topographies were characterized experimentally and were implemented in the model free from any additional fitting parameters using a modified Maxwell–Garnett theory. Finally, the model was shown to predictively assess the experimentally measured effects of temperature on the prism sensitivity.