Here, it is studied the surface plasmon resonance phenomenon on indium tin oxide (ITO) coated optical fibers as a function of the ITO thin film properties. These novel fiber-optic SPR devices overcome the major drawbacks of the traditional prism based Kretschmann configuration due to the optical fiber setup. On the other hand, the utilization of ITO improve the traditional disadvantages of the gold or silver layer based configurations, such as quenching of the fluorescence, oxidation or hard to process surfaces. In addition, the utilization of ITO coated optical fibers as the SPR supporting substrates, shifts the resonance wavelength to the IR and near-IR region of the spectrum as well as allows the resonance wavelength tunability by adjusting the ITO fabrication parameters.

These devices were fabricated via a dip-coating process as explained by Ota etal using 200 mm fused silica optical fiber core (Thorlabs Inc.) as substrate. The deposition process was stopped at 8 dips (S1 devices) and 10 dips (S2 devices) in order to obtain ITO coatings with different properties and thicknesses of 85 and 115 nm respectively.

The absorbance spectra collected at the end of the fiber were recorded when the sensitive region was immersed in different glycerin/water concentrations from 0% to 85% corresponding to refractive index from 1.333 and 1.450 respectively.

In conclusion, these novel fiber-optic SPR based on ITO coating have been proven as a useful tool in order to determine the refractive index of the external medium in contact with the ITO layer. Furthermore, the resonance wavelength has been proven to be sensitive to variations in the ITO properties.

The authors acknowledge financial support to the Spanish Ministry of Education and Science-FEDER TEC2006-12170

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