Perfluorinated polymer optical fiber tapers for fluorescencecollection

摘要

We propose the use of perfluorinated cladded multimode polymer optical fibers tapers for fluorescent detection inaqueous environment. A graded-index polymer optical fiber with core and cladding diameters of 62.5/90 and very lowrefractive index (nCore = 1.356, nCladding = 1.342) has been used. The taper has been fabricated using the heat-and-pull technique. Despite to the fact that taper core is not in direct contact with the external medium, this fiber taper can beused for sensing applications. In fact, some of the guided modes are no more confined in the core region but can still beguided by the fiber in the cladding region. Therefore, in the taper region, there is an evanescent wave in the externalmedium, related to the cladding modes. The taper geometry and the very low refractive index of the material core-cladding (1,35-1,34) permits a strong enhancement of the penetration depth increasing the fluorescence collectionefficiency in aqueous environments (1.33). Fluorescence measurements in an aqueous solution containing Cy5 dye in aconcentration range 3.14x10-7M to 6.76x10-6M have been performed.