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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - FOMBIST (Fibre-Optic Multi-parametric BIochemical Sensing Technology)

Teaser

Summary

Bio/chemical sensors, hugely involved in industrial production, medicine and scientific research, a magnitude range of bio/chemical parameters such as glucose and uric acid concentration in human body blood are lacking appropriate monitoring tools capable of multi-parametric measurement in real time for control of quality, effectiveness and cost.
Traditional ways of monitoring are mostly based on chemical approaches which are inaccurate and complex, requiring sampling and are not in favour of industrial request for real-time, remote, label-free and in-situ monitoring. Optical fibre sensing technique, on the other hand, is a promising alternative due to its unparalleled advantages over chemical, electronic and interferometer counterparts: immunity to electric-magnetic field interference, compact size, low power consumption, high sensitivity, low electric sparks risk, adaptable in harsh environments, capable of remote monitoring and highly secured, multiplexing in wavelength and time domain. It is the ultimate aim of FOMBIST to exploit the novel titled fibre grating technologies for highly sensitive multi-parametric monitoring of bio/chemical processes, combining the fellowâ€™s bio/chemical sensing background with advanced photonic and bio/chemical expertise of the EU hosts.
Through this project, with the help of the main host Aston Institute of Photonic Technologies (AIPT), the Fellow, Dr. Jiang have developed many kinds of optical fibre device for photonic multi-parametric sensing technologies as expected contributed to the internationally academic communities and industries. The Fellow have gained the skills including fibre grating design and fabrication (at AIPT), UV laser micro-fabrication, optical fibre interferometry, nano-film sensing technologies.

Work performed

1) We proposed and demonstrated a carbon nanotube (CNT)-modified microfiber Bragg grating (MFBG) to measure the refractive index with a strong enhancement of the sensitivity in the low refractive index region. The introduction of the CNT layer influences the evanescent field of the MFBG and causes modification of the reflection spectrum. The experimental results disclose that the CNT-MFBG demonstrates strong sensitivity in the low refractive index range of 1.333-1.435, with peak intensity up to -53.4 dBm/refractive index unit, which is 15-folds higher than that of the uncoated MFBG. Therefore, taking advantage of the CNT-induced evanescent field enhancement, the reflective MFBG probe presents strong sensing capability in biochemical fields.
2) We investigated the polarization modulation properties of a hybrid waveguide of graphene integrated excessively tilted fibre grating (Ex-TFG), by exploiting the polarization-sensitive coupling effect of graphene with the optical mode. The theoretical analysis and experimental results demonstrate that the real and imaginary parts of complex refractive index of few layer graphene exhibit different effects on transverse electric (TE) and transverse magnetic (TM) cladding modes of the Ex-TFG, enabling stronger absorption in the TE mode and more wavelength shift in the TM mode. Furthermore, the surrounding refractive index can modulate the complex optical constant of graphene and then the polarization properties of the hybrid waveguide, such as resonant wavelength and peak intensity. Therefore, the unique polarization tuning property induced by the integration of the graphene layer with Ex-TFG may endow potential applications in all-in-one fibre modulators, fibre lasers, and biochemical sensors.
3) We presented a refractometer with main- and vernier-scale to measure the refractive index (RI) of liquids with high precision by using the fine spectrum structure of a TFBG. The main- and vernier-scale are calibrated by measuring large groups of fine spectra at different cut-off mode resonances in a small RI range, and the use of vernier-scale certainly reduces the RI measurement uncertainty resulted from the discrete cladding mode resonances. The performance of the TFBG-based vernier refractometer is experimentally verified by exploring the temperature dependence of RI of anhydrous ethanol in a near infrared region, showing an enhanced accuracy to the order of 10-4, high repeatability and temperature self-calibration capability.
4) We proposed a label-free biosensor based on graphene oxide (GO) and glucose oxidase (GOD) functionalized tiltedfiber grating (TFG) with large tilted angle for low concentration glucose detection. Surface characterizations with optical microscopy, scanning electron microscopy, Raman and infrared spectroscopy provide detailed assessments and evidences about the homogeneity of GO deposition and the effectiveness of enzyme modification. The detection results of the low-concentration glucose demonstrate that the resonant wavelength has a linear response to the glucose concentration in the range of 0-8 mM with a response coefficient of âˆ¼0.24 nm/mM, showing an enhanced sensitivity and bio-selectivity compared with the pristine TFG.
5) A high-sensitivity curvature sensing configuration is implemented by using a fiber Mach-Zehnder interferometer (MZI) with D-shaped fiber Bragg grating (FBG). A segment of D-shaped fiber is fusion spliced into a single mode fiber at both sides, and then a short FBG is inscribed in the D-shaped fiber. The fiber device yields a significant spectrum sensitivity as high as 87.7 nm/m-1 to the ultra-low curvature range from 0 to 0.3 m-1, and can distinguish the orientation of curvature experienced by the fiber as the attenuation dip producing either a blue or red wavelength shift, by virtue of the asymmetry of D-shaped fiber cladding. In addition, by tracking both resonant wavelengths of the MZI and embedded FBG, the temperature and curvature can be

Final results

1. some new photonic devices and novel sensing technologies, such as graphene-integrated excessively TFGs, enzymatic graphene oxide-functionalized TFG, â€œvernierâ€ TFBG, and in-line MZI with D-shaped fibre grating, are proposed to EU with understanding of their principle and applicability. The research carried out in this project will not only help the development of biology, chemistry, medicine, but also encourage relevant areas such as environment, food, industrial process and aerospace.
2. The novel sensors such as TFG-based glucose sensors developed by this project will provide an advanced tool capable of real-time, remote operation and with more precision for tackling the food safety, biomedical diagnostics.
3. The miniaturized size and remote label-free sensing capacity of the proposed glucose sensing device permit a multitude of opportunities for single-point measurement in harsh conditions and hard-to-reach spaces, presenting a promising candidate for label-free glucose detection for disease diagnosis, pharmaceutical research and bioengineering applications.