This paper explores how a fluorescent dye can be immobilized in a polymer film at the distal end of an optical fibre to serve as a fibre optical chemical sensor for organic solvents in water. The sensing principle is based on a shift in the fluorescence peak of the dye.
The mid-IR wavelength range, and the fundamental vibrational absorption fingerprint region it encompasses, can be utilised for a variety of environmental and medical monitoring applications requiring the detection of specific covalently bonded molecules, for example, in atmosphere or in a patient’s breath. Mid-IR transmitting chalcogenide fibres, based on the elements: sulfur, selenium, and tellurium, have a characteristically high optical non-linearity and thus can be tailored to also generate mid-IR supercontinuum light that covers this fingerprint region.
The process of designing, fabricating, and characterising chalcogenide glass fibres via differential scanning calorimetry, microscopy, ellipsometry, and optical fibre loss measurements is detailed.
We demonstrate a robust photoacoustic medium for measuring the concentration of ammonia in an aqueous solution. We target the near-infrared (NIR) overtone absorption band (~1540 nm) of ammonia with a supercontinuum (SC) laser-based excitation system and an immersion-based acoustic transducer as the detection system. We further present how such a simple system can be used to perform effective in-situ measurements of ammonia over a range of concentrations with a sensitivity of parts per million (ppm) by volume and linearity of <96%. We demonstrate how the sensing system can be readily tailored to monitor the concentrations of other miscible gases in the aqueous solution.
In this work, we report a cost-effective supercontinuum (SC) laser-based multispectral photoacoustic spectroscopy (MSPAS) system for studying spectral characteristics of various analytes. We demonstrate an in vitro label-free monitoring of the analytes in the extended near-infrared (NIR) (1540–1840 nm) spectral range. We further demonstrate how a simple ratiometric analysis in conjunction with linear regression can be used for accurate prediction of glucose over commonly encountered physiological levels inside the human body (0–400 mg/dL). Looking forward, the proposed SC-based MSPAS system provides a framework for the development of label-free and non-invasive monitoring multiple bio-analytes accurately, with potential translation to clinical in vivo applications.
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