Fiber optics and photonics : emerging applications - introduction to the feature issue

Author name used in this publication: H. Y. TamVersion of RecordPublishe

Polarization-maintaining photonic-crystal-fiber-based all-optical polarimetric torsion sensor

Author name used in this publication: P. K. A. WaiAuthor name used in this publication: H. Y. TamAuthor name used in this publication: C. Lu2010-2011 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Simple temperature insensitive fiber Bragg grating based tilt sensor with enhanced tunability

Author name used in this publication: H. Y. Tam2011-2012 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Pressure sensor realized with polarization-maintaining photonic crystal fiber-based Sagnac interferometer

Author name used in this publication: H. Y. TamAuthor name used in this publication: Li-Yang ShaoAuthor name used in this publication: P. K. A. WaiAuthor name used in this publication: C. Lu2007-2008 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Optical sensors based on polymeric nanofibers layers created by electrospinning

Porous materials have become ideal candidates for the creation of optical sensors that are able to reach extremely high sensitivities, due to both the possibility to infiltrate the target substances on them and to their large surface-to-volume ratio. In this work, we present a new alternative for the creation of porous optical sensors based on the use of polymeric nanofibers (NFs) layers fabricated by electrospinning. Polyamide 6 (PA6) NFs layers with average diameters lower than 30 nm and high porosities have been used for the creation of Fabry-Pérot optical sensing structures, which have shown an experimental sensitivity up to 1060 nm/RIU (refractive index unit). This high sensitivity, together with the low production cost and the possibility to be manufactured over large areas, make NFs-based structures a very promising candidate for the development of low-cost and high performance optical sensors.The Spanish government (TEC2015-63838-C3-1-R-OPTONANOSENS); Basque government (KK-2017/00089-μ4F)

Fibre optic absorbance meter with low limit of detection for waterborne cations

We report an evanescent wave based fibre optic absorbance meter that enables the colorimetric detection of waterborne cations with water insoluble chromoionophoric sensitisers. This establishes an alternative to the PVC membrane based transducers that are conventionally used for this purpose. Here, a water insoluble sensitiser is coated as a thin film on an unclad section of a multimode optical fibre to overlap with the evanescent field of a light beam propagating along the fibre core. The colorimetric response of the sensitiser when in contact with waterborne cation leads to increased absorption of virtual photons associated with the evanescent field. The resulting intensity loss of the propagating beam is detected by a bespoke newly designed self- referenced evanescent wave absorbance meter with beam intensity modulation and Lock-in amplification. We validate our transducer with the well characterised water insoluble sensitizer, 1-(2-pyridylazo)-2-naphthol (PAN), for the detection of aqueous Zn2+ cations. We find a limit of detection (LoD) of 54 nM Zn2+, 28 times lower compared to a PVC membrane based sensor using same sensitiser for same cation (Albero et al., Journal of Pharmaceutical and Biomedical Analysis 29 (2002), 779). Our evanescent wave absorbance meter can easily be adapted to other colorimetric sensitisers, including chromoionophoric complex forming macrocycles

Chemical tapering of polymer optical fiber

Polymer optical fibers (POFs) have significant advantages over numerous sensing applications. The key element in developing sensor is by removing the cladding of the fiber. The use of organic solvent is one of the methods to create tapered POF in order to expose the core region. In this study, the etching chemicals involved is acetone, methyl isobutyl ketone (MIBK), and acetone-methanol mixture. The POF is immersed in 100%, 80%, and 50% of acetone and MIBK dilution. In addition, the mixture of acetone and methanol is also used for POF etching by the ratio 2:1 of the volume. Acetone has shown to be the most reactive solvent towards POF due to its fastest etching rate compared to MIBK and acetone-methanol mixture. The POF is immersed and lifted from the solution for a specific time, depending on the power loss properties for the purpose of producing unclad POF. In comparison to silica fiber optic, the advantages of POF in terms of its simple technique and easy handling enable it to produce unclad POF without damaging the core region. The surface roughness of the POF is investigated under the microscope after being immersed into different solvent. This method of chemical tapering of POF can be used as the fundamental technique for sensor development. Next, the unclad fiber is immersed into ethanol solutions in order to determine the reaction of unclad POF towards its surrounding. The findings show that this particular sensor is sensitive towards concentration changes ranging between 10 wt% to 50 wt%