MODEL OF A CHEMO-OPTICAL SENSOR BASED ON PLASMON EXCITATION IN THIN SILVER FILMS

A more realistic theoretical model of a chemo-optical sensor based on the resonant excitation of surface plasma waves is presented here. First, the fundamental sensing configuration, consisting of an optical glass prism, a metal film, a sensing layer and the environment, is analysed. Optical parameters of Ag films obtained by our attenuated total reflection (ATR) measurements are employed in this analysis. The optical behaviour of the bromocresol purple sensing layer is simulated using published data. Such a choice of the sensing layer enables this structure to be used for sensing basic vapours in the air. A more general sensing configuration with an added layer is then analysed. For this purpose a new more realistic figure of merit of sensitivity is defined. Some specific features of this configuration are discussed and special attention is given to the utilization of this added layer to increase the sensitivity of the sensor.