Hairul A Abdul-Rashid | Multimedia University (original) (raw)

Papers by Hairul A Abdul-Rashid

Bulletin of the American Physical …, 2007

We assume the creation of a blackhole[1] in a physical universe. We now conjecture that the black... more We assume the creation of a blackhole[1] in a physical universe. We now conjecture that the blackhole will then separate itself from the physical universe and build up an extra dimensional entity associated with the physical universe. We postulate this extra dimensional entity is ...

F1000Research, 2021

Background: One way to reduce the length of the gain medium in Erbium-Doped Fiber Amplifier (EDFA... more Background: One way to reduce the length of the gain medium in Erbium-Doped Fiber Amplifier (EDFA) is by doping the fiber core with a high concentration of Erbium. However, this method caused ion clustering effects, which limits the EDFA’s efficiency. In this research, the use of Gallium as a new co-dopant in erbium-doped silica fiber is explored. Methods: The new fiber, namely Gallium co-doped Erbium fiber (Ga-EDF), is used as a gain medium in an optical fiber amplifier setup. A 2-meter length of the Ga-EDF fiber was used in a single pass configuration with a forward pumping scheme at 150 mW pump power. The Ga-EDF amplifier's gain and noise figure while pumping at 980 nm and 1480 nm were compared. The amplifier's performance was evaluated as the input signal power varied between -30 dBm to 3 dBm, over the wavelength range of 1520 nm to 1580 nm. Results: The 980 nm-pumped Ga-EDF amplifier achieved the maximum small-signal gain of 22.45 dB and the corresponding noise figure ...

IEEE Photonics Journal, 2020

In this paper, we review the highly promising silica glass, fabricated as doped and undoped optic... more In this paper, we review the highly promising silica glass, fabricated as doped and undoped optical fiber for intended use in radiation dosimetry. The dosimetry techniques reviewed here, underpinned by intrinsic and extrinsic defects in silica glass, focus on Thermoluminescence (TL), Optically Stimulated Luminescence (OSL) and Radioluminescence (RL), with occasional references to the much more established Radiation Induced Attenuation (RIA). The other focus in this review is on the various materials that have been reported earlier as dopants and modifiers used in silica glass optical fiber radiation dosimeters. This article also elaborates on recently reported optical fiber structures, namely, cylindrical fibers, photonic crystal fibers and flat fibers, as well as dimensions and shapes used for optimization of dosimeter performance. The various types of optical fiber radiation dosimeters are subsequently reviewed for various applications ranging from medical dosimetry such as in external beam radiotherapy, brachytherapy and diagnostic imaging, as well as in industrial processing and space dosimetry covering a dynamic dose range from μGy to kGy. Investigated dosimetric characteristics include reproducibility, fading, dose response, reciprocity between luminescence yield to dose-rate and energy dependence. The review is completed by a brief discussion on limitations and future developments in optical fiber radiation dosimetry.

Applied Radiation and Isotopes, 2015

In regard to thermoluminescence (TL) applied to dosimetry, in recent times a number of researcher... more In regard to thermoluminescence (TL) applied to dosimetry, in recent times a number of researchers have explored the role of optical fibers for radiation detection and measurement. Many of the studies have focused on the specific dopant concentration, the type of dopant and the fiber core diameter, all key dependencies in producing significant increase in the sensitivity of such fibers. At doses of less than 1Gy none of these investigations have addressed the relationship between dose response and TL glow peak behavior of erbium (Er)-doped silica cylindrical fibers (CF). For x-rays obtained at accelerating potentials from 70 to 130kVp, delivering doses of between 0.1 and 0.7Gy, present study explores the issue of dose response, special attention being paid to determination of the kinetic parameters and dosimetric peak properties of Er-doped CF. The effect of dose response on the kinetic parameters of the glow peak has been compared against other fiber types, revealing previously misunderstood connections between kinetic parameters and radiation dose. Within the investigated dose range there was an absence of supralinearity of response of the Er-doped silica CF, instead sub-linear response being observed. Detailed examination of glow peak response and kinetic parameters has thus been shown to shed new light of the rarely acknowledged issue of the limitation of TL kinetic model and sub-linear dose response of Er-doped silica CF.

2011 2nd International Conference on Photonics, 2011

... A.Mansoor*, YN Phua, M. Othman, Nurul Shahrizan Shahabuddin and Z. Yusoff Senior Member IEEE ... more ... A.Mansoor*, YN Phua, M. Othman, Nurul Shahrizan Shahabuddin and Z. Yusoff Senior Member IEEE Center of Advanced Devices and Systems, Faculty of Engineering, Multimedia University, 63100, Cyberjaya ... [2] MH Al-Mansoori, B. Rouzid, BM Ali, MK Abdullah and MA Mahdi ...

IEEE Communications Letters, 2006

The authors investigate semi-analytically the optimized system performance limitation in an SCM-W... more The authors investigate semi-analytically the optimized system performance limitation in an SCM-WDM passive optical network (PON) in the presence of cross phase modulation (XPM) and group velocity dispersion (GVD). A general expression for electrical average crosstalk noise power due to XPM and GVD was derived to measure the system performance for increasing number of WDM channels. Using the expression, we show that XPM and GVD causes crosstalk in the system and imposes a power penalty as the WDM channels increases for a given channel spacing and modulating frequency. These results are extended to show that the system can be optimized to achieve a minimum BER of 10 −9 by controlling the channel spacing and modulating frequency as the number of WDM channels increases.

2020 IEEE 8th International Conference on Photonics (ICP), 2020

The strain magnification effect on the conventional single mode fiber (SMF) is investigated by us... more The strain magnification effect on the conventional single mode fiber (SMF) is investigated by using solid mechanics module in COMSOL Multiphysics. The strain effect is measured by applying the hydrostatic pressure on the SMF. In this paper, different coating materials and the position of the SMF in the coating are investigated. The investigation of the strain magnification effect on the SMF by COMSOL will help to produce the best coating's parameters of SMF which suits well in distributed pressure sensing application.

Radiation Physics and Chemistry, 2015

Laser Physics, 2014

This work proposes a new method to enhance the performance of an S-band fiber laser by using a th... more This work proposes a new method to enhance the performance of an S-band fiber laser by using a thulium-doped photonic crystal fiber (PCF). The proposed method is based on amplified spontaneous emission (ASE) suppression provided by the thulium-doped PCF unique geometric structure. The enhanced performance of this filter based PCF is dependent on the short and long cut-off wavelength characteristics that define the fiber transmission window. Realizing the short wavelength cut-off location requires the PCF cladding to be doped with a high index material, which provides a refractive index difference between the core and cladding region. Achieving the long cut-off wavelength necessitates enlarging the size of the air holes surrounding the rare-earth doped core region. The PCF structure is optimized so as to achieve the desired ASE suppression regions of below 0.8 μm and above 1.8 μm. The laser performance is simulated for different host media, namely pure silica, alumino-silicate, and fluoride-based fiber ZBLAN based on this thulium-doped PCF design. The host media spectroscopic details, including lifetime variations and quantum efficiency effect on the lasing emission are also discussed. Information on the filter based PCF design is gathered via a full-vectorial finite element method analysis and specifically a numerical modelling solution for the energy level rate equation using the Runge–Kutta method. Results are analyzed for gain improvement, lasing cavity, laser efficiency and effect of core size diameter variation. Results are compared with conventional thulium-doped fiber and thulium-doped PCF for every single host media. We observe that the ZBLAN host media is the most promising candidate due to its greater quantum efficiency.

Optical Fiber Technology and Applications, 2021

Plasmonics

ABSTRACT This paper presents the representation circuit model for Fano resonance of plasmonic nan... more ABSTRACT This paper presents the representation circuit model for Fano resonance of plasmonic nanoparticles in the optical domain. An intuitive explanation is provided for the physical nature of Fano resonance based on the three-level quantum system, and the Fano resonance effects of three basic nanoparticle arrangements, namely tetramer, pentamer, and symmetry broke pentamer are discussed. A coupling capacitor is calculated as an equivalent component in the proposed circuit model in order to describe the coupling effect between subradiant and superradiant mode in the Fano resonance. The circuit impedances of tetramer, pentamer, and broken symmetry pentamer are simulated, with resultant circuit models in agreement with the calculated results based on S-parameters.

Radiation Physics and Chemistry, 2016

The supralinearity of GFF and TLD-100 was highly dependent on the UHD. The maximum supralinearity... more The supralinearity of GFF and TLD-100 was highly dependent on the UHD. The maximum supralinearity f(D)max of TLD-100, occurs around 10 kGy. TL kinetic model can be used to explain the glow peak behavior of doses o f(D)max. The supralinearity response decreases for doses above the critical dose limit. a b s t r a c t The thermoluminescence (TL) response of Germanium Flat Fiber (GFF) and TLD-100 irradiated with 2.5 MeV electrons for the doses up to 1 MGy were studied and compared. The aim was to evaluate the TL supralinearity response at an ultra-high dose (UHD) range and to investigate the change in kinetic parameters of the glow peaks, as the doses increases up to 1 MGy. It is found that the critical dose limit (CDL) of GFF is 5 times higher as compared to TLD-100. CDL is determined by the dose at the maximum supralinearity, f(D) max. It is also found that annealing the TLD-100 and GFF with temperature more than 400 °C is required to reset it back to its original condition, following radiation doses up to 1 MGy. It is also noticed the strange behavior of Peak 4 (TLD-100), which tends to be invisible at the lower dose (o10 kGy) and starts to be appeared at the critical dose limit of 10 kGy. This result might be an important clue to understand the behavior of TLD-100 at extremely high dose range. For both samples, it is observed that the TL intensity is not saturated within the UHD range studied.

Applied Optics, 2015

Grating inscription in a Ga-doped silica core fiber (∼5 wt. % Ga) has been demonstrated using Ar... more Grating inscription in a Ga-doped silica core fiber (∼5 wt. % Ga) has been demonstrated using ArF (193 nm) and KrF (248 nm) excimer lasers. In a comparative study with germanosilicate fiber with similar Ge concentration, a Ga-doped silica core fiber shows greater photosensitivity to an ArF excimer laser due to the higher absorbance in the region of 190-195 nm. In addition, the photosensitivity of a Ga-doped silica core fiber has been greatly enhanced with hydrogenation. Ga-doped fibers are potential photosensitive fibers for fiber Bragg grating production with an ArF excimer laser.

Optical Transmission Systems and Equipment for WDM Networking, 2002

2014 IEEE 5th International Conference on Photonics (ICP), 2014

The fabrication of Tm/Al-doped silica preforms by an improved MCVD method with metal chelate prec... more The fabrication of Tm/Al-doped silica preforms by an improved MCVD method with metal chelate precursors is discussed. Two fabrication techniques are employed, namely; simultaneous soot-dopant deposition (or standard MCVD) and stepwise soot-dopant deposition. The preforms are characterized by refractive index profiler and EPMA. The results show that the stepwise soot-dopant technique has a higher incorporation of Al2O3 and Tm2O3 as compared to the simultaneous soot-dopant method. This is due to the drawbacks of our chelate delivery system such as the temperature gradient and flow design. For the stepwise technique, the measured index difference of the preform is 0.006 with 0.8 wt% (maximum) Tm incorporated in the core.

Radiation Physics and Chemistry, 2014

The Ge dopant in commercially available silica optical fibres gives rise to appreciable thermolum... more The Ge dopant in commercially available silica optical fibres gives rise to appreciable thermoluminscence (TL), weight-for-weight offering sensitivity to MV X-rays several times that of the LiF dosimeter TLD100. The response of these fibres to UV radiation, X-rays, electrons, protons, neutrons and alpha particles, with doses from a fraction of 1 Gy up to 10 kGy, have stimulated further investigation of the magnitude of the TL signal for intrinsic and doped SiO2 fibres. We represent a consortium effort between Malaysian partners and the University of Surrey, aimed at production of silica fibres with specific TL dosimetry applications, utilizing modified chemical vapour deposition (MCVD) doped silica-glass production and fibre-pulling facilities. The work is informed by defect and dopant concentration and various production dependences including pulling parameters such as temperature, speed and tension; the fibres also provide for spatial resolutions down to <10 µm, confronting many limitations faced in use of conventional (TL) dosimetry. Early results are shown for high spatial resolution (~0.1 mm) single-core Ge-doped TL sensors, suited to radiotherapy applications. Preliminary results are also shown for undoped flat optical fibres of mm dimensions and Ge-B doped flat optical fibres of sub-mm dimensions, with potential for measurement of doses in medical diagnostic applications.

Journal of Optics A: Pure and Applied Optics, 2006

A new method to measure the modulator chirp parameter is proposed. This method will be performed ... more A new method to measure the modulator chirp parameter is proposed. This method will be performed in two steps. In the first step, the frequency separation between two optical signals passing through a phase conjugator is changed. This produces a resonance reference frequency as a result of the accumulated fibre chromatic dispersion (CD). In the second step, a RF modulated