Fibre optic refractive index microsensor based on white-light SPR excitation

We have developed a fibre-optic microsensor for refractive index measurements and used it with a biological application. It is targeting a refractive index range for aqueous environments between 1.30 and 1.36 and a spatial resolution of below I mm. The sensing element consists of a single-ended tapered optical fibre that is coated with a 50 nm gold layer. White light is coupled into the fibre and excites surface plasmon resonance (SPR) at the fibre tip. The reflected light is measured with a spectrometer and then converted to refractive index units (RIU). The presented sensor measures the refractive index in the range of 1.30-1.38 RIU with an accuracy of 2 x 10(-4) RIU. (C) 2004 Elsevier B.V. All rights reserved.