Air-suspended solid-core fibers for sensing

摘要

Microstructured optical fibers have the potential to provide improved performance relative to more traditionalspectroscopic fiber sensors. In fact the manipulation of the geometry of the fiber cross section can allow tomaximize the interaction of light and sample. Recently, solid air-suspended core fibers have been appointed asthe most promising design for evanescent field sensing. In this kind of device, sensing is carried out through theinteraction between evanescent tails of index-guided modes and sample, which fills cladding holes. Suspendedcore fibers are made by three silica webs joining in the fiber center and forming the core. This design canprovide an evanescent field power fraction greater than any other structure previously proposed, together witha wide transmission band. In this paper, the electromagnetic field behaviour of the guided modes of a rangeof suspended-core fibers is investigated, using a full-vectorial finite element based modal solver. The impact ofdifferent design parameters and materials on guidance, the amount of power in the cladding and the possibilityof obtaining effective single-mode guidance are also investigated.