We investigate the potential of microstructured optical fibers (MOFs) for highly sensitive absorption and fluorescence measurements by infiltrating a dye solution in the holey structure. Generally in a MOF only the evanescent part of the electromagnetic field penetrates into the sample material, providing a weak light-matter interaction. We compare such a MOF with a selectively filled hollow core photonic crystal fiber (HCPCF), in which most of the field energy propagates in the sample material. We show that dye concentrations down to 1×10-10 M can be detected in a HCPCF using only nanoliter sample volumes. Our experiments proof that HCPCFs are well suited for demanding sensing applications, outperforming existing fiber tools that rely on evanescent sensing.
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