Surface-plasmon sensor for absorption-sensitivity enhancement.

A method to enhance the absorption sensitivity of a sample by utilizing surface-field enhancement with surface-plasmon resonance is proposed. The experimental setup is based on the configuration for the attenuated total internal reflection (ATR) method but with a thin metal film deposed on the substrate prism. The mechanism responsible for the sensitivity enhancement is analyzed theoretically; the best thickness for the metal film to have to attain optimum enhancement is numerically calculated. Experimental results are shown in which the proposed method compared with the conventional ATR method exhibits the sensitivity enhancement of the absorption measurement. The sensor applications for this technique are also discussed.