Mohamad Halim Abd. Wahid
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Preferred name
Mohamad Halim Abd. Wahid
Official Name
Mohamad Halim, Abd. Wahid
Alternative Name
Wahid, M. H.A.
Wahid, Mohamad Halim Abdul
Main Affiliation
Scopus Author ID
5478542340
Researcher ID
DTC-0242-2022

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UWB triplet and quadruplet pulses generation employs nonlinear effect in semiconductor optical amplifier nonlinear loop mirror

2020-01-08 , Zahari, Suhaila Mohd , Mohamad Halim Abd. Wahid , Nor Azura Malini Ahmad Hambali , Nurjuliana Juhari , Ghazali N.F. , Shahimin M.M.

Ultrawideband (UWB) triplet and quadruplet pulses generation exploits nonlinear effect in semiconductor optical amplifier (SOA) in nonlinear loop mirror (NOLM) is investigated in this work. Two signals are transmitted through the SOA-NOLM simultaneously to create cross-phase modulation (XPM) effect. Firstly, the XPM causes the production of doublet which later combines for creation of triplet and quadruplet. This technique engages a proper tuning of optical delay and a selection of suitable power in all loops. Besides, injection current of the SOAs also governs the formation of these pulses. Although, frequency of the signals can be varied accordingly, the pulses are limited to certain adjustment that shifted its position in time domain. Furthermore, the set up can also be assessed for monocycle and doublet pulses by extracting the output at several positions. It can be concluded that the design may work as multiple pulses generation. All pulses are examined and compared with their electrical spectrum counterpart for validity of this approach.

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Thermal analysis of LED packaging with single-walled carbon nanotube heat sink

2023 , Chu Kok Keong , Nor Azura Malini Ahmad Hambali , Mohamad Halim Abd. Wahid , H. Mohamad , Norshamsuri Ali @ Hasim

The thermal issue is still the bottleneck of a light emitting diode (LED) system to sustain its operational performance. In this paper, we design, simulated, and analysed an LED packaging with single walled carbon nanotubes as a heat sink. The 5W LED packaging is simulated with different types of LED chips materials which comprise gallium nitride, indium nitride, zinc oxide, zinc selenide and titanium dioxide. Using LED chips materials as the heat source, the heat flow is conducted through the bottom layer to the heat sink and dissipates by convection or radiation heat transfer to the surrounding. The addition of thin film on top of the phosphorus layer functions to enhance the recombination rate and guided the flow of heat to the bottom. The 5W titanium dioxide light emitted diode packaging (LED packaging C) has been successfully demonstrated to have overall temperature reduced to around ~10°C by using single walled carbon nanotube heat sink as compared to copper heat sink and aluminium heat sink. Meanwhile, carbon material as thermal interface material and substrate also plays a major role as a thermal cooling solution in LED packaging. For 5W titanium dioxide light emitted diode packaging, under self-heating conditions, the maximum average temperature generated is 81.05 °C. Despite that, under convection conditions, the maximum average temperature generated is 41.53°C.

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Loop Mirror Multi-wavelength Brillouin Fiber Laser Utilizing Semiconductor Optical Amplifier and Fiber Bragg Grating

2017-02-01 , Najwa Idris , Nor Azura Malini Ahmad Hambali , Mohamad Halim Abd. Wahid , Ariffin N. , Shahimin M. , Mohd. Azarulsani Md. Azidin

In this paper, the development of loop mirror multi-wavelength Brillouin fiber laser utilizing semiconductor optical amplifier and fiber Bragg grating is successfully demonstrated. A multi-wavelength BFL structure employs a single mode fiber that acts as the gain medium, while the fiber Bragg grating act to reflect the signals and semiconductor optical amplifier is used to amplify the signal are employed to produce multiple channels. The implementation of difference parameter for semiconductor optical amplifier driven current, Brillouin pump power, Brillouin pump wavelength and length of single mode fiber, plays an important role in producing the multiple channels. The highest number of channels which is 15 achieved once 9 km of SMF length, semiconductor optical amplifier current at 800mA and low Brillouin pump power at-12 dBm are utilized in the laser structure. Furthermore, the implementation of semiconductor optical amplifier and reflectivity of fiber Bragg grating in Brillouin fiber laser structure gives a better performance in producing the multiple channels.

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Design of arrayed waveguide grating (AWG) demultiplexer based PMMA for narrow channel spacing

2020-01-08 , Nurjuliana Juhari , Yusof, Muhammad Fadzliazuan , Mohamad Halim Abd. Wahid , Nur Syakimah Ismail

Arrayed Waveguide Grating (AWG) based PMMA polymer that functioning as multiplexer/demultiplexer (mux/de-mux) having good potential in WDM system and interferometer optical sensor. Besides, AWG is suitable for larger count optical signals and good filter response devices. AWG demultiplexer based polymer was simulated using Beam Propagation Method (BPM) under TE mode with 1550 nm central wavelength. This work explores the performance of polymer-based AWG with straight waveguide structure that capable to produce 16-channels AWG device for 100 GHz (0.8 nm) channel spacing. The 16-channels AWG based polymer produces low insertion loss of 3.430 dB and low crosstalk of -24.763 dB. The central wavelength for each output port gives almost similar values with the standard ITU-T DWDM wavelength grid with the smallest difference of 0.5 nm. This proposed device also capable to solve the demand on higher channel capacity especially to support internet usage and the needs of the best communication system.

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Gigahertz repetition rate ultrashort laser pulses from coherent external Fabry-Pérot cavity

2020-01-08 , Chan, Tian Seng , Mohamad Halim Abd. Wahid , Prabakaran A/L Poopalan

Transient analysis of ultrashort laser pulses (USP) output from a coherent external Fabry-Pérot cavity (CEFPC) comprising a group delay dispersion (GDD) balanced ultrafast Bragg reflector and a negative dispersion double-chirped mirror for sub-terahertz repetition rate generation is investigated. Analytical results manifest a low multiplication factor (MF) of the CEFPC with value equal to any non-integer, real number greater than unity (NIRNGU) could lead to the amplitude varying, transient timing-jitter, but at very high constant repetition rate (frep-o-Constant) USP output pulse train. For the configuration - (MF) TaeFP = TaUSP-in, where MF is a NZRNGU, the MF is not a factor which usually describes the relationship between the frep-o and frep-i, but rather a factor which determines the correlation of USPs TUSP-in and TeFP. Besides, this mentioned configuration is proven to be more easily to generate a CW, high frep-o USP train (>10GHz) at steady-state, compared to the conventional configuration with MF equal to a non-zero positive integer, which requires a much shorter external cavity length to generate a similar high frep-o USP train.

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Characterization of all-optical Tofolli and Peres gates employing optimized SOA-NOLM

2020-01-08 , Nur Hafizah Ghazali , Mohamad Halim Abd. Wahid , Nor Azura Malini Ahmad Hambali , Nurjuliana Juhari , Zahari S.M. , Shahimin M.M.

In this work, all-optical reversible gates namely Tofolli and Peres are studied and characterized. The gates utilize semiconductor optical amplifier (SOA) in nonlinear loop optical mirror (NOLM). The reversible gates are performed at data rate 10 Gb/s with narrow Gaussian pulses as input signals. Delay of 130 ps and injection current of 170 mA have displayed the optimum outputs in the SOA-NOLM. Extinction ratio is greatly reduced, thus less noise interferes the logic operation in this simple technique. It is observed that Peres gate has shown a higher output power compare to Toffoli gate. This could be due to multiple amplification that are experienced by the signals. Other than the gain, injection current and delay are shown to give major effect in producing the correct bits at the outputs. The SOA-NOLM also can be cascaded for other arithmetic signal processing operation at high frequency. It is also recorded that the design consumes low power especially in small signal gain process. Thus, the design indicates its versatility to be executed in photonic integrated circuits for ultrafast signal control through fiber networks.

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The structure and optical properties of Lithium Niobate grown on quartz for photonics application

2017 , Makram A. Fakhri , Mohamad Halim Abd. Wahid , Suad M. Kadhim , Ban A. Badr , Evan T. Salim , Uda Hashim , Zaid T. Salim

This paper focuses on the structure and optical properties of Lithium niobate (LN) deposited on quartz substrate by sol-gel method. The solution was prepared at different molarity concentration and annealed at 500 °C. The LNs were analyzed by UV-visible, X-ray diffraction (XRD) and Scanning Electron Microscope (SEM). The results show that as the molar concentration increases, the films crystallization becomes more atomically distributed and the energy band gap approaches 4 eV. Transmission spectra were taken in the wavelength range of 400-1100 nm. Hexagonal structure was observed with good atoms distribution and homogeneous crystallization. There were two phases of LNs recorded in this work.

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A sight of view on electrical impacts, structural properties and surface roughness of tungsten trioxide thin film: effect of substrate temperatures in WO₃/Si device fabrication

2023 , Evan T Salim , Azhar I Hassan , Farhan A Mohamed , Mohamad Halim Abd. Wahid , Makram A Fakhri

Monoclinic WO₃ thin films have been effectively deposited by a simple spray pyrolysis technique at a molar concentration of 0.01 M on a glass substrate in the temperature range of 473 to 673 K. These WO₃ films were used as an interlayer between the metal and the semiconductor, which formed the basic structure of the photodetector. Effect of substrate temperature on WO₃ films during the process of the deposition was systematically interpreted with respect to the structural, morphological, optical and electrical properties of the WO₃ films. The x-ray diffraction pattern revealed the polycrystalline nature of the prepared films with monoclinic phases. At the substrate temperature of 623 K, the nano-thin films were strongly bonded to each other as observed from the FE-SEM images. Visible and ultraviolet spectroscopies indicated the band gap (Eg) of the WO₃ thin film is 3.30 eV. The dc electrical study recorded a sharp increase in the electrical conductivity of the prepared film at substrate temperature of 623 K for tungsten trioxide. It is worth noting that all diodes showed a positive photoresponse under illumination. In particular, the photodetector with the thickness of 300 nm showed higher responsivity 0.02 A/W and detection specificity 8.29 × 1010 Jones.

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Multiwavelength fiber laser employing semiconductor optical amplifier in nonlinear optical loop mirror with polarization controller and polarization maintaining fiber

2020-01-08 , Husshini N.F.H. , Nor Azura Malini Ahmad Hambali , Mohamad Halim Abd. Wahid , Shahimin M.M. , Mohd Najib Mohd Yasin , Norshamsuri Ali @ Hasim , Al-Asadi H.A.A. , Raghavendra C.G.

This paper demonstrates multiwavelength fiber laser employing semiconductor optical amplifier in nonlinear optical loop mirror with polarization controller and polarization maintaining fiber. The configuration consists of a 3-dB coupler, polarization controller and several lengths of polarization maintaining fiber. The results showed a single polarization controller with 5 meters of polarization maintaining fiber length generated 36 of lasing lines at 160mA of semiconductor optical amplifier current. In addition, for the average peak power and average optical signal to noise ratio, the 2 meters of polarization maintaining fiber length with single polarization controller in the nonlinear optical loop mirror shows higher values, 0.55mW at 210mA and 31.98dB at 210mA, respectively. Both gain media have a wider bandwidth operating in the C-band and L-band at room temperature.

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Characteristics of multiwavelength fiber laser employing semiconductor optical amplifier in nonlinear optical loop mirror with different length polarization maintaining fiber

2020-01-08 , Husshini N.F.H. , Nor Azura Malini Ahmad Hambali , Mohamad Halim Abd. Wahid , Shahimin M. , Mohd Najib Mohd Yasin , Norshamsuri Ali @ Hasim , Al-Asadi H.A.A.

In this paper, we propose and demonstrate generated characteristics of a multiwavelength fiber laser based on semiconductor optical amplifier in a nonlinear optical loop mirror with different length of polarization maintaining fiber. The configuration comprises 3-dB optical coupler, semiconductor optical amplifier and, 2 meters and 10 meters of polarization maintaining fiber. Characteristics of multiwavelength fiber laser are studied through the use of polarization maintaining fiber at different lengths. The experimental results revealed the number of lasing lines increases with the increment of the polarization maintaining fiber length. The polarization maintaining fiber with 10 meters of length has the ability to generate a higher number of lasing lines up to 47 signals with semiconductor optical amplifier injected current at 180mA, respectively. However, in terms of average peak power and average optical signal to noise ratio, the 2 meter of polarization maintaining fiber length has the capability to produce a higher value which is 0.45mW at 250mA of semiconductor optical amplifier driven current and 28.86dB at 170mA of semiconductor optical amplifier driven current, respectively. Furthermore, it is observable that this configuration capable to generate a wider bandwidth which is operating in the conventional (C) band to long (L) band at the room temperature.

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