In this paper, a tapered tip optical fiber probe sensor for localized refractive index (RI) measurements is presented. This sensor’s interaction with analytes is confined to a few micro-meters which makes it a promising candidate for in-vivo or even intra-cellular RI monitoring. This tapered tip was simply fabricated by etching optical fiber with hydrofluoric acid to a conic shape with a sub-micrometer aperture. The sensor was calibrated for RI measurement using different concentrations of NaCl in water. Limit of detection of 6.7×10^-5 RIU was achieved for this low-cost sensor.

Keywords: etching, intra-cellular sensor, optical fiber tip, refractive index, tapered optical fiber

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