Abstract
We present improvements to fluorescence sensing in soft-glass microstructured optical fibers that result in significantly improved sensitivity relative to previously published results. Concentrations of CdSe quantum dots down to 10 pM levels have been demonstrated. We show that the primary limitation to the sensitivity of these systems is the intrinsic fluorescence of the glass itself.
Highlights
Optical fibers are ideal for environmental sensing applications because of their ability to transmit optical signals to and from the sensing region without the use of free-space optics
A spectrum was taken of the unfilled fiber to ensure consistency between results to eliminate any possible variations in the signal arising from cleave-related reductions in the coupling efficiency, and the fiber filled with quantum dots (Qdots) for a range of different concentrations
These results demonstrate that with a relatively high input power of 2.5 μW for all measurements, the minimum detectable Qdot signal using this configuration is
Summary
Optical fibers are ideal for environmental sensing applications because of their ability to transmit optical signals to and from the sensing region without the use of free-space optics. Microstructured optical fibers (MOFs) are suited to such applications as the air spaces inside the fiber form natural cavities for locating the material to be detected These types of fibers have a significant advantage over conventional core-clad fibers, in that they can be fabricated from a single material, so issues involving thermal and chemical compatibility between different glasses can be avoided [2]. By tailoring both the MOF material and the geometry, the light-matter overlap can be increased to values much larger than with conventional fibers. We employ the suspended nanowire design [10] that provides the high evanescent overlap of a standard nanowire [11] with the large interaction length and robust handling comparable to conventional fibers
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