DEVELOPMENT OF A SURFACE-PLASMON RESONANCE SENSOR FOR COMMERCIAL APPLICATIONS

An optical tabletop system based on surface plasmon resonance (SPR) fo r refractive-index determination has been developed to demonstrate the feasibility of a miniaturized and integrated concept which is also de scribed. The tabletop system is constructed from the 'miniaturizable' components required to realize a manufacturable, integrated minisensor utilizing the SPR phenomenon for transduction. The tabletop system ex hibits adequate sensitivity, stability, and reproducibility while main taining overall system simplicity. The sensor system is excited by a n ear-infrared light-emitting diode (LED) available in die form, since a laser source is impractical for the miniaturized sensor. The light is optically coupled into a plastic prism because the minisensor optics are readily molded using plastics or epoxy, rather than glass. The ang ular composition of the diverging reflected radiation is then separate d and quantified by a photodiode array (also available in die form) co nsisting of pixels on a 63 mu m pitch. A sputtered gold film is used a s the SPR excitation layer. The sensor system performance is qualified using aqueous solutions containing ethylene glycol. The response to c hanges in concentration of the ethylene glycol is found to be on the o rder of one part in 10(4), This translates to a refractive-index chang e of approximately 10(-5). The stability of the system response has be en investigated by quantifying the response change in water over a two -day period. The stability is excellent when temperature compensation is implemented. The components utilized in the tabletop system are con sistent with the development of a low-cost miniature integrated surfac e plasmon sensor. Such a device has been constructed. A sketch of a mi nisensor is shown, along with preliminary response data.