The Experts below are selected from a list of 22008 Experts worldwide ranked by ideXlab platform
D A Bradley - One of the best experts on this subject based on the ideXlab platform.
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different germanium dopant concentration and the thermoluminescence characteristics of flat ge doped Optical Fibres
2017Co-Authors: Muhammad Safwan Ahmad Fadzil, D A Bradley, N M Ung, Noramaliza Mohd NoorAbstract:The influence of elevated germanium concentration on the thermoluminesence characteristics of a novel form of fabricated flat Optical fibre was examined. All the samples were irradiated with two nominal photon energies (6 MV and 10 MV) and 1.25 MeV gamma energy. Flat Fibres with 10 mol % Ge concentration provided the superior TL yield compared against that of 6 and 8 mol % Ge-doped Optical Fibres for both 6 MV and 10 MV energy. Interpretation of the results has been aided by study of the glow curves, revealing in particular new generation of defects in the flat Fibres due to strain-generation at the collapsed surfaces. The strain represent deep-energy defects.
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glass beads and ge doped Optical Fibres as thermoluminescence dosimeters for small field photon dosimetry
Physics in Medicine and Biology, 2014Co-Authors: S M Jafari, D A Bradley, Amani I Alalawi, M Hussein, W Alsaleh, M A Najem, R P HugtenburgAbstract:An investigation has been made of glass beads and Optical Fibres as novel dosimeters for small-field photon radiation therapy dosimetry. Commercially available glass beads of largest dimension 1.5 mm and GeO2-doped SiO2 Optical Fibres of 5 mm length and 120 µm diameter were characterized as thermoluminescence dosimeters. Results were compared against Monte-Carlo simulations with BEAMnrc/DOSXYZnrc, EBT3 Gafchromic film, and a high-resolution 2D-array of liquid-filled ionization chambers. Measurements included relative output factors and dose profiles for square-field sizes of 1, 2, 3, 4, and 10 cm. A customized Solid-Water® phantom was employed, and the beads and Fibres were placed at defined positions along the longitudinal axis to allow accurate beam profile measurement. Output factors and the beam profile parameters were compared against those calculated by BEAMnrc/DOSXYZnrc. The output factors and field width measurements were found to be in agreement with reference measurements to within better than 3.5% for all field sizes down to 2 cm2 for both dosimetric systems, with the beads showing a discrepancy of no more than 2.8% for all field sizes. The results confirm the potential of the beads and Fibres as thermoluminescent dosimeters for use in small photon radiation field sizes.
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establishment of ge doped Optical Fibres as thermoluminescence dosimeters for brachytherapy
Applied Radiation and Isotopes, 2012Co-Authors: Fatma Issa, D A Bradley, R P Hugtenburg, A Nisbet, Ahmad Taufek Abdul RahmanAbstract:Abstract This study aims to establish the sensitive, ∼120 μm high spatial resolution, high dynamic range Ge-doped Optical Fibres as thermoluminescence (TL) dosimeters for brachytherapy dose distribution. This requires investigation to accommodate sensitivity of detection, both for the possibility of short range dose deposition from beta components as well as gamma/x-mediated dose. In-air measurements are made at distances close to radionuclide sources, evaluating the fall off in dose along the transverse axis of 133 Ba and 60 Co radioactive sources, at distances from 2 mm up to 20 mm from their midpoints. Measurements have been compared with Monte Carlo code DOSRZnrc simulations for photon-mediated dose only, agreement being obtained to within 3% and 1% for the 133 Ba and 60 Co sources, respectively. As such, in both cases it is determined that as intended, beta dose has been filtered out by source encapsulation.
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thermoluminescence responses of photon and electron irradiated ge and al doped sio2 Optical Fibres
Chinese Physics Letters, 2012Co-Authors: Husin Wagiran, D A Bradley, I Hossain, A N H Yaakob, T RamliAbstract:We carry out a comparison of the thermoluminescence (TL) response of photon and electron irradiated Ge- and Al-doped SiO2 Optical Fibres, as well as cross-comparison with that of TLD-100. Irradiation is made with 6 MeV electrons and 6 MV photons, for doses ranging from 0.2 Gy to 4.0 Gy. The commercially available Al- and Gedoped Optical Fibres produce a linear dose-TL response. The TL yield for both of the doped Fibres and also for TLD-100 is greater for electron irradiation than for photon irradiation. The TL yield of the Al-doped Fibres is a small fraction of that of Ge-doped Fibres (by a factor of 25), the Ge-doped Fibres offering a response of 59% of that of TLD-100.
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ge doped Optical Fibres as thermoluminescence dosimeters for kilovoltage x ray therapy irradiations
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2011Co-Authors: Fatma Issa, D A Bradley, Nur Atiqah Abd Latip, A NisbetAbstract:Abstract We investigate key dosimetric parameters for the thermoluminescence (TL) of Ge-doped silica Optical Fibres irradiated by X-rays generated at 90 and 300 kVp. The parameters include dose response, reproducibility and fading. Relative dose measurements were performed, obtaining central axis percentage depth dose (PDD) values, use being made of doped Fibres irradiated in water and solid water phantoms. TL yields were compared with published data and ionisation chamber measurements. Linearity to dose was demonstrated over the investigated range (0.1–6 Gy), with reproducibility to within±2%. TL fading was found to be minimal, at
F. Poletti - One of the best experts on this subject based on the ideXlab platform.
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Exceptional polarization purity in antiresonant hollow-core Optical Fibres
Nature Photonics, 2020Co-Authors: A. Taranta, E. Numkam Fokoua, S. Abokhamis Mousavi, J. R. Hayes, T. D. Bradley, G. T. Jasion, F. PolettiAbstract:High-performance interferometers, gyroscopes, frequency combs, quantum information experiments and Optical clocks rely on the transmission of light beams with the highest possible spatial and polarization purity. Free-space propagation in vacuum unlocks the ultimate performance but becomes impractical at even modest length scales. Glass Optical Fibres offer a more pragmatic alternative, but degrade polarization purity and suffer from detrimental nonlinear effects. Hollow-core Fibres have been heralded for years as the ideal compromise between the two, but achieving high modal purity in both spatial and polarization domains has proved elusive thus far. Here, we show that carefully designed, low-nonlinearity hollow-core antiresonant Fibres can transmit a single pair of orthogonal polarization modes with cross-coupling on the scale of 10^–^10 m^–^1; that is, orders of magnitude lower than any other solution. This free-space-like Optical guidance can immediately provide a leap in performance for photonics-enabled sensors and instruments. Carefully designed hollow-core antiresonant Fibres support a pair of orthogonal polarization modes with a level of purity and cross-coupling that is orders of magnitude lower than other fibre designs and beyond the fundamental Rayleigh scattering limit of glass core Fibres.
Maryanne C. J. Large - One of the best experts on this subject based on the ideXlab platform.
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strain sensing using long period gratings in microstructured polymer Optical Fibres
21st International Conference on Optical Fibre Sensors (OFS21), 2011Co-Authors: Richard Lwin, Alexander Argyros, Sergio G Leonsaval, Maryanne C. J. LargeAbstract:We investigate the use of long period gratings inscribed in single-mode microstructured polymer Optical Fibres for strain sensing. A simple inscription technique allows gratings to be inscribed with features at visible wavelengths, matching the transmission window of PMMA. Tracking of the grating features allows strains from 0.05% to over 20% to be detected, and the inscription of multiple gratings in the same fibre at different wavelengths allows for the possibility of distributed sensing.
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opening up Optical Fibres
Optics Express, 2007Co-Authors: Felicity Cox, Maryanne C. J. Large, Richard Lwin, Cristiano M B CordeiroAbstract:A unique Optical fibre design is presented in this work: a laterally accessible microstructured Optical fibre, in which one of the cladding holes is open to the surrounding environment and the waveguide core exposed over long lengths of fibre. Such a fibre offers the opportunity of real-time chemical sensing and biosensing not previously possible with conventional microstructured Optical Fibres, as well as the ability to functionalize the core of the fibre without interference from the cladding. The fabrication of such a fibre using PMMA is presented, as well as experimental results demonstrating the use of the fibre as a evanescent wave absorption spectroscopy pH sensor using the indicator Bromothymol Blue.
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microstructured polymer Optical Fibres
2007Co-Authors: Martijn A Van Eijkelenborg, N.a. Issa, S. Manos, Joseph Zagari, Ross C. Mcphedran, S Fleming, Maryanne C. J. Large, Alexander Argyros, Ian Bassett, Martijn C. De SterkeAbstract:The first microstructured polymer Optical fibre is described. Both experimental and theoretical evidence is presented to establish that the fibre is effectively single moded at Optical wavelengths. Polymer-based microstructured Optical Fibres offer key advantages over both conventional polymer Optical Fibres and glass microstructured Fibres. The low-cost manufacturability and the chemical flexibility of the polymers provide great potential for applications in data communication networks and for the development of a range of new polymer-based fibre-optic components.
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microstructured polymer Optical Fibres new opportunities and challenges
Molecular Crystals and Liquid Crystals, 2006Co-Authors: Maryanne C. J. Large, Narahari S. Pujari, Martijn A Van Eijkelenborg, Alexander Argyros, Richard Lwin, Ian Bassett, Surendra Ponrathnam, G W BartonAbstract:ABSTRACT Microstructured polymer Optical Fibres [mPOF] were first developed in 2001, and have attracted attention in part because the range of fabrication techniques possible with polymers has allowed novel structures to be made that cannot be made simply in other materials. Their material properties also offer attractive possibilities as polymers can contain a much larger variety of dopants than glass. In this article, we review progress on some of the major challenges of this technology: particularly the need to reduce fibre losses, and report on some recent developments including the fabrication of the first hollow core mPOF. Some initial investigations into changing the material properties are reviewed.
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cleaving of microstructured polymer Optical Fibres
Optics Communications, 2006Co-Authors: J D Harvey, R J Kruhlak, Martijn A Van Eijkelenborg, M Song, E. Wu, G W Barton, Maryanne C. J. LargeAbstract:The issue of how best to cleave PMMA microstructured polymer Optical Fibres (mPOF) is addressed. The impact of the following parameters on the cleaving process is considered: (i) temperature of the cutting blade, (ii) temperature of the platen holding the fibre, (iii) time allowed for thermal equilibration between fibre and platen, (iv) blade speed, and (v) blade condition. The strong influence of a temperature-dependent phase transition in the polymer on the cleaving process is established. Optically acceptable mPOF end-faces can be achieved but only over a limited range of cleavage conditions.
Julien Fatome - One of the best experts on this subject based on the ideXlab platform.
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polarization domain walls in Optical Fibres as topological bits for data transmission
Nature Photonics, 2017Co-Authors: M Gilles, Pierreyves Bony, Josselin Garnier, Antonio Picozzi, Massimiliano Guasoni, Julien FatomeAbstract:Domain walls are topological defects that occur at symmetry-breaking phase transitions. Although domain walls have been intensively studied in ferromagnetic materials, where they nucleate at the boundary of neighbouring regions of oppositely aligned magnetic dipoles, their equivalents in optics have not been fully explored so far. Here, we experimentally demonstrate the existence of a universal class of polarization domain walls in the form of localized polarization knots in conventional Optical Fibres. We exploit their binding properties for Optical data transmission beyond the Kerr limits of normally dispersive Fibres. In particular, we demonstrate how trapping energy in a well-defined train of polarization domain walls allows undistorted propagation of polarization knots at a rate of 28 GHz along a 10 km length of normally dispersive Optical fibre. These results constitute the first experimental observation of kink–antikink solitary wave propagation in nonlinear fibre optics. Localized polarization knots formed in conventional Optical Fibres are shown to be able to act as topological bits of information for Optical data communication.
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polarization domain walls in Optical Fibres as topological bits for data transmission
Nature Photonics, 2017Co-Authors: M Gilles, Pierreyves Bony, Josselin Garnier, Antonio Picozzi, Massimiliano Guasoni, Julien FatomeAbstract:Domain walls are topological defects which occur at symmetry-breaking phase transitions. While domain walls have been intensively studied in ferromagnetic materials, where they nucleate at the boundary of neighbouring regions of oppositely aligned magnetic dipoles, their equivalent in optics have not been fully explored so far. Here, we experimentally demonstrate the existence of a universal class of polarization domain walls in the form of localized polarization knots in conventional Optical Fibres. We exploit their binding properties for Optical data transmission beyond the Kerr limits of normally dispersive Fibres. In particular, we demonstrate how trapping energy in well-defined train of polarization domain walls allows undistorted propagation of polarization knots at a rate of 28 GHz along a 10 km length of normally dispersive Optical fibre. These results constitute the first experimental observation of kink-antikink solitary wave propagation in nonlinear fibre optics.
Husin Wagiran - One of the best experts on this subject based on the ideXlab platform.
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thermoluminescence responses of photon and electron irradiated ge and al doped sio2 Optical Fibres
Chinese Physics Letters, 2012Co-Authors: Husin Wagiran, D A Bradley, I Hossain, A N H Yaakob, T RamliAbstract:We carry out a comparison of the thermoluminescence (TL) response of photon and electron irradiated Ge- and Al-doped SiO2 Optical Fibres, as well as cross-comparison with that of TLD-100. Irradiation is made with 6 MeV electrons and 6 MV photons, for doses ranging from 0.2 Gy to 4.0 Gy. The commercially available Al- and Gedoped Optical Fibres produce a linear dose-TL response. The TL yield for both of the doped Fibres and also for TLD-100 is greater for electron irradiation than for photon irradiation. The TL yield of the Al-doped Fibres is a small fraction of that of Ge-doped Fibres (by a factor of 25), the Ge-doped Fibres offering a response of 59% of that of TLD-100.
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low dose photon irradiation response of ge and al doped sio2 Optical Fibres
Applied Radiation and Isotopes, 2011Co-Authors: Nor Haliza Yaakob, D A Bradley, Ahmad Termizi Ramli, Husin Wagiran, Md Imam Hossain, Hasan AliAbstract:We have investigated the thermoluminescent response and fading characteristics of germanium- and aluminium-doped SiO2 Optical Fibres. These Optical Fibres were placed in a solid phantom and irradiated using 6 and 10 MV photon beams at doses ranging from 0.02 to 0.24 Gy delivered using a linear accelerator. In fading studies, the TL measurements were continued up to 14 days post-irradation. We have investigated the linearity of TL response as a function of dose for Ge-, Al-doped Optical fibre and TLD-100 obtained for 6 and 10 MV photon irradiations. We have concentrated on doses that represent a small fraction of that delivered to the tumour to establish sensitivity of measurement for peripheral exposures in external beam radiotherapy.
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electron irradiation response on ge and al doped sio2 Optical Fibres
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2011Co-Authors: Nor Haliza Yaakob, D A Bradley, Ahmad Termizi Ramli, Husin Wagiran, I Hossain, Suhairul HashimAbstract:Recently, research groups have reported a number of radiation effects on the applications of SiO2 Optical Fibres with possible use as dosimeter material because these Optical fibre provide a good basis for medical radiation dosimetry. The objective of this study is to investigate the thermoluminescence response and fading characteristic for germanium and aluminium doped SiO2 Optical Fibres with photon irradiation. These Optical Fibres are placed in solid phantom and irradiated to 6 and 10 MV photon beam at dose ranging from 0.06 Gy to 0.24 Gy using Primus MLC 3339 linear accelerator at Hospital Sultan Ismail, Johor Bahru. In fading studies, the TL measurements were continued up to 14 days period. The Optical Fibres will produce glow curves whereby the information is then analyzed. Al and Ge-doped Optical Fibres have a linear dose-TL signal relationship that is proportionality between the TL signal and the doses. Comparison for TL response between different linear accelerator showed a good agreement because these Optical Fibres also have a linear dose-TL signal relationship even using different equipments.
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the thermoluminescence response of oxygen doped Optical Fibres subjected to photon and electron irradiations
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2010Co-Authors: S Hashim, D A Bradley, Ahmad Termizi Ramli, Nianhua Peng, Husin WagiranAbstract:Abstract The work describes an attempt to increase the thermoluminescence (TL) yield of pure silica Optical Fibres, introducing oxygen concentrations through to a depth of 160 nm by means of an ion implantation technique. Subsequent investigation of TL yield was performed by irradiating the O 2 -doped Optical Fibres to 6 MV photons and separately to 6, 9 and 12 MeV electrons. To allow comparison, equivalent irradiations were also performed on Ge- and Al-doped silica and pure silica (Ps) Fibres, the TL response of these being the subject of previous investigations. The results show the superior TL response to be that of the Ge-doped Optical Fibres followed by that of the O 2 -doped Fibres. As an example, at 6 MV for doses of up to 4 Gy, the response of the Ge-doped Fibres was found to be four times that of the O 2 -doped Fibres, while the response of the O 2 -doped Fibres was around 68 times that produced by the Al-doped Fibres. As a consequence of the variability of defect concentration obtained in the process of ion implantation, the O 2 -doped Fibres showed greater fluctuation in dose response than the Ge-doped Fibres. O 2 -doped Fibres are observed to provide promising sensitivity on first use, subsequent annealing leading to the loss of practically all added dopants.
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the thermoluminescence response of doped sio2 Optical Fibres subjected to fast neutrons
Applied Radiation and Isotopes, 2010Co-Authors: S Hashim, D A Bradley, M. Iqbal Saripan, Ahmad Termizi Ramli, Husin WagiranAbstract:This paper describes a preliminary study of the thermoluminescence (TL) response of doped SiO2 Optical Fibres subjected to 241AmBe neutron irradiation. The TL materials, which comprise Al- and Ge-doped silica Fibres, were exposed in close contact with the 241AmBe source to obtain fast neutron interactions through use of measurements obtained with and without a Cd filter (the filter being made to entirely enclose the Fibres). The neutron irradiations were performed for exposure times of 1-, 2-, 3-, 5- and 7-days in a neutron tank filled with water. In this study, use was also made of the Monte Carlo N-particle (MCNPTM) code version 5 (V5) to simulate the neutron irradiations experiment. It was found that the commercially available Ge-doped and Al-doped Optical Fibres show a linear dose response subjected to fast neutrons from 241AmBe source up to seven days of irradiations. The simulation performed using MCNP5 also exhibits a similar pattern, albeit differing in sensitivity. The TL response of Ge-doped fibre is markedly greater than that of the Al-doped fibre, the total absorption cross section for Ge in both the fast and thermal neutrons region being some ten times greater than that of Al.
