LIST OF CONTRIBUTED PAPERS
CONTRIBUTED PAPERS
Rizal Ramli*, Mohd Saiful Dzulkefly Zan
Pulse fiber lasers are recent developments that produce efficient pulse lasers by incorporating gain medium, saturable absorber (SA) materials and SA hosts. However, the SA hosts can be improved for stable generation pulse fiber laser. This discussion emphasizes the fabrication and characterisation of tapered and arc-shaped fiber using the flame-brushing and wheel polishing technique, respectively. Examples of using tapered fiber and arcshaped fiber to generate Q-switched and mode-locked will be deliberated that can possibly be applied in communications, medicine and sensing.
Abdulfatah A. G. Abushagur*, Siti Azlida Ibrahim, Zulfadzli Yusoff, Ahmad Ashrif A. Bakar
A label-free optical biosensor presents an innovative solution for biochemical detection, besides tapered optical fiber (TOF), Tilted fiber Bragg gratings (TFBGs) have been shown to have distinctive properties that enable the creation of highly precise sensors, especially in biochemical realm, while maintaining cost efficiency in both manufacturing and signal interrogation. This review compares both the TFBGs and TOF, Emphasizing the latest developments in their fabrication techniques, sensing mechanisms, and limitations. Most recent achievements of both will be discussed through examples from the literature. Pros and cons will be assessed and discuss the potential advantages of combining both structures.
Norhafizah Burham, Muhammad Amir Syazwan Tukiman, Naimah Mat Isa, Aziati Husna Awang*
Formaldehyde (CH₂O) is a toxic, colourless, and flammable gas that is widely used in various industries and household products. Current formaldehyde detection methods often suffer from limitations such as low sensitivity, high cost, and impracticality for widespread use in residential and industrial settings. This study focuses on evaluating the performance of uncoated and Rhenium Disulfide (ReS₂)-coated tapered optical fibers (TOFs) in detecting formaldehyde, using fibers with a waist diameter of 10 µm and a length of 3 mm. The experimental evaluation was conducted by exposing the TOFs to formaldehyde vapor concentrations of 1%, 2%, 3%, 4%, and 5%, under relative humidity conditions ranging from 30% to 90%. The results show that the ReS₂-coated TOFs demonstrated better sensitivity in detecting formaldehyde compared to uncoated TOFs with measured sensitivities of – 0.03245 dBm/% and –0.00371 dBm/% at 5% formaldehyde concentration. Overall, formaldehyde sensing performance can be improved by coating the TOFs with ReS₂, with sensitivity increasing by more than 80% compared to the uncoated fibers.
Muhammad Qayyum Othman*, Athiyah Sakinah Masran, Azween Hadiera Hishamuddin, Mohd Hafiz Abu Bakar, Nur Hidayah Azeman, Nadhratun Naiim Mobarak, Ahmad Ashrif A Bakar
Chlorine contamination in crude palm oil (CPO) is a key factor in the formation of 3monochloropropane-1,2-diol (3-MCPD), a harmful contaminant with carcinogenic potential. Existing detection methods such as ion chromatography (IC) and total chlorine analyzers (TCA) are accurate but complex, time-consuming, and not suitable for rapid or on-site testing. This study was conducted to develop a localized surface plasmon resonance (LSPR) optical sensor for detecting organic chlorine in edible oil matrices. The main objectives of this study are to investigate LSPR sensing for chlorine detection, fabricate a composite-based LSPR sensor using succinyl-functionalized nanocarbon quantum dots (succinyl-NCQD) and silver nanotriangles (AgNT), and evaluate its sensitivity in detecting low chlorine concentrations. Succinyl-NCQD was chosen as the sensing material to improve binding interaction and signal response. The sensor showed a strong linear response in the 0.5–5 ppm range with a sensitivity of 1.6877 nm ppm−1, a limit of detection (LOD) of 0.56 ppm, and a limit of quantification (LOQ) of 1.85 ppm.
Azween Hadiera Hishamuddin*, Ahmad Sabirin Zoolfakar, Mohd Hafiz Abu Bakar, Fairuz Abdullah, Nur Hidayah Azeman, Ahmad Ashrif A Bakar, Maizatul Zolkapli
This study presents an enhanced oxygen detection method combining fluorescence sensing with surface plasmon resonance (SPR) using a multimode polymer optical fiber (POF). The POF is coated with a silver layer for SPR and the palladium-based dye PdTFPP, known for its high oxygen sensitivity. PdTFPP alone showed an emission peak at 668.62 nm, with intensity decreasing as oxygen concentration increased. The SPR-enhanced sensor showed a sensitivity of 0.1045 compared to 0.0944 for PdTFPP alone, demonstrating improved performance.
Athiyah Sakinah Masran*, Nur Hidayah Azeman, Nur Afifah Ahmad Nazri, Azween Hadiera Hishamuddin , Mohd Hafiz Abu Bakar , Muhammad Qayyum Othman , Rozita Sulaiman , and Ahmad Ashrif A Bakar
The detection of creatinine, a crucial biomarker for kidney function, has attracted significant attention due to the need for rapid and sensitive detection. In this study, we report a comparative analysis of Carbon Dots (CDs) and Carboxyl-Carbon Dots (CDsCOO) for developing a fluorescent based creatinine sensor. Both carbon dots were synthesized via a hydrothermal approach, with surface modification introduced to generate carboxyl functional groups in CDsCOO. Creatinine sensing performance was evaluated based on the fluorescence quenching response, calibration curve linearity, sensitivity, and limit of detection (LOD). The effectiveness of this material was evaluated at concentrations ranging from 0 to 0.6 mg/dL. The CDsCOO demonstrated superior performance with enhanced sensitivity and a lower LOD than unmodified CDs, achieving a LOD of approximately (0.05 mg/dL & 0.28 mg/dL) and a sensitivity of 20.123 nm/mg/dL & 3.696 nm/mg/dL. This work highlights the potential of CDsCOO as a promising platform for efficient and selective creatinine detection.
Rozita Sulaiman*, Nur Hidayah Azeman, Athiyah Sakinah Masran, Muhammad Qayyum Othman , Nur Afifah Ahmad Nazri , Azween Hadiera Hishamuddin, Mohd Hafiz Abu Bakar , and Ahmad Ashrif A Bakar
Accurate nutrient determination is crucial for optimizing hydroponic systems. Traditional methods like electrical conductivity (EC), ion-selective electrodes (ISE), and colourimetry are hindered by limited ion specificity, high maintenance, and prolonged analysis times. Spectroscopy-based AI methods often demand extensive sample sets, limiting their real-time applicability. This study presents a rapid UV-VisNIR spectroscopy technique integrated with machine learning (ML) for predicting nitrogen and phosphorus levels using minimal samples. Among five regression models tested Support Vector Machine Regression (SVR), Linear Regression (LR), Partial Least Squares Regression (PLSR), Random Forest Regression (RFR), and Gradient Boosting Trees Regression (GBTR), linear regression (LR) excelled for nitrogen prediction (R2=0.9734; RMSE=19.2345 ppm), although its performance slightly dropped during external validation (R2=0.923; RMSE=30.6666 ppm). Random forest regression (RFR) showed superior accuracy for phosphorus prediction (R2=0.9578, 0.9468). Integration of Support Vector machine (SVM) classification with LR and RFR further improved accuracy (R2=0.96), even with just 26 samples. This ML-based spectroscopy model enables rapid, precise nutrient monitoring, enhancing crop yield and sustainability in hydroponics.
Muhammad Muhsin Kalilur Raheem*, Hafiz Zulhazmi Jabidin, Wan Muhammad Noor Haekal W Mamat, Ain Nabihah Mohammad Rihan, Mohd Saiful Dzulkefly Zan
Phase-sensitive optical time-domain reflectometry (Φ-OTDR) has emerged as a powerful technique for distributed acoustic sensing (DAS) in a wide range of applications, including perimeter security. The signal-to-noise ratio (SNR) is a critical parameter in determining the sensitivity and reliability of vibration detection in these systems. In this paper, we present a detailed analysis of SNR performance in Φ-OTDR-based DAS systems. We investigate the influence of key system parameters such as optical pulse width, vibration frequencies and spatial resolution on the SNR value. A DAS setup is developed to evaluate how these parameters affect the backscattered signal and noise characteristics over pulse widths and vibration frequencies. Our results show that SNR increases exponentially with optical pulse widths, but it degrades the spatial resolution value. The findings provide practical insights into the phase information in the development of a more efficient and sensitive DAS system. This work contributes to the growing understanding of SNR limitations and enhancement strategies in distributed fiber optic sensing.
Norhanis Aida Mohd Nor*, Waan Nur Amierha Wan Ibrahim
Gallium nitride (GaN) light-emitting diodes (LEDs) are essential for visible light communication (VLC), enabling high-speed data transmission and energy-efficient lighting. However, c-plane GaN LEDs face limitations due to polarization fields and the quantumconfined Stark effect (QCSE), restricting bandwidth and data rates. Advances in semi-polar and non-polar GaN structures have enhanced bandwidth, supporting gigabit-per-second VLC performance. Optimizing the active region through quantum well thinning and hybrid quantum dot integration further boosts modulation speeds. Additionally, Europium (Eu³⁺) doping provides high-color-purity red emission and faster recombination, improving bandwidth and reducing efficiency droop. This review highlights these innovations for high-speed VLC systems.
Aziati Husna Awang, Muhammad Afiq Aiman Mazlan, Norazida Ali, Naimah Mat Isa, Norhafizah Burham*
This study investigates the influence of tapered optical fiber diameter and MoS₂ concentration on the sensitivity of optical humidity sensors fabricated using the heat-and-pull method. Optical fibers with tapered diameters of 3 µm, 5 µm, and 7 µm were analyzed under varying humidity levels (40%, 50%, and 60%). Additionally, the effect of different MoS₂ concentrations 2 µl, and 4 µl coated on the fiber surface was examined for each diameter. Experimental results demonstrate that smaller fiber diameters yield significantly higher sensitivity, with the 3 µm fiber showing the greatest power response at all humidity levels, with up to 35.07% more sensitivity at 40% humidity compared to 7 µm fibers. Furthermore, increasing MoS₂ concentration enhances the sensor response across all diameters, with the 4 µl concentration consistently delivering the highest power output. For example, at 40% humidity, a 4 µl concentration on a 7 µm fiber produced an 18.89% increase in sensitivity compared to an uncoated fiber.
Nur Afifah Ahmad Nazri*, Nur Hidayah Azeman, Nurul Izzah Zakaria, Muhammad Asif Ahmad Khushaini, Mohd Hafiz Abu Bakar, Tengku Hasnan Tengku Abdul Aziz, Ahmad Ashrif A Bakar, and Ahmad Rifqi Md Zain
This study presents a comparative SPR analysis of tetrahydrothiophene (THT) and benzo[b]thiophene-2-carboxaldehyde (BTCA) as sensing layers for creatinine detection. Using an SPR setup, both materials exhibited concentration-dependent spectral shifts. The BTCA-based sensor demonstrated higher sensitivity (3.3557 nm/(mg/dL)), better linearity (R2 = 0.9636), and lower detection limits than THT, attributed to stronger molecular interactions, including hydrogen bonding and dipole-dipole effects. These results confirm BTCA's superior plasmonic response, supporting its potential as a label-free sensing material for creatinine detection in clinical diagnostics.
Ain Nabihah Mohammad Rihan*, Intan Fatimah Sasila Ghadzali, Saiful Dzulkefly Zan, Yosuke Tanaka and Norhana Arsad
We propose an independent real spectral analysis method to improve the Brillouin frequency shift (BFS) resolution using the differential cross-spectrum technique (DCS-BOTDR). The proposed method only considers the real components to extract BGS. For a 1.2 km test fiber length, we have achieved 0.4 m spatial resolution, 1.98 MHz Brillouin frequency accuracy, and 1.025 MHz/°C temperature sensitivity using the proposed method.
Intan Fatimah Sasila Ghadzali*, Mohd Saiful Dzulkefly Zan, Ain Nabihah Mohammad Rihan
Accurate extraction of the Brillouin Frequency Shift (BFS) is vital for high-performance distributed fiber sensing, particularly under noisy or low-resolution conditions. This study presents a robust machine learning approach using the AdaBoost regression algorithm to extract BFS from Brillouin Gain Spectra (BGS) under challenging spectral scenarios, including low signal-to-noise ratio (SNR), limited frequency range, and coarse resolution. Experimental BGS data were obtained from a Differential-Cross Spectrum (DCS) BOTDR setup based on the correlation of two optical pulses, measured over a temperature range of 25°C to 70°C. To enhance model generalization, synthetic noisy datasets were generated through data augmentation, and Savitzky-Golay filtering was applied to preserve spectral peak structure. The results demonstrate the model’s robustness and highlight the importance of maintaining high SNR, sufficient frequency coverage, and fine resolution for reliable BFS extraction in practical sensing environments.
Hikmat Maad, Norita Mohd Yusoff, Siti Barirah Ahmad Anas, Makhfudzah Mokhtar, Mohd Adzir Mahdi, and Zuraidah Zan*
We demonstrate dissipative soliton resonance (DSR) mode-locking using a nonlinear amplifying loop mirror (NALM) in a C-band erbium-doped fiber (EDF) laser. The mode-locked laser achieved 3-dB spectral bandwidth of 24.56 nm centered at 1562.7 nm, with an output power of 5.0 mW and a pulse energy of 16.81 nJ. The DSR pulse tunability was optimized, where the pulse width was extended from 20 ns to 140 ns, demonstrating enhanced performance with a repetition rate of 297.3 KHz. The optimization was achieved through figure-of-eight NALM cavity design, precise polarization control, and progressive pump power tuning under net anomalous dispersion.
Long Muhammad Haziq Long Hassan, Seri Mastura Mustaza and Norhana Arsad*
Distributed Acoustic Sensing (DAS) and geophone technologies are implemented for seismic monitoring with limited comparative analysis between these systems particularly in integrating data from heterogeneous sensors. One of raising in utilization of advanced machine learning for seismic data classification. Data fusion is promising solution, which capable of combining information from multiple sources to improve accuracy and robustness of seismic interpretation. Hence, in this study focus on integrating DAS and geophone data using data fusion by utilizing unsupervised machine learning with K-Means clustering to classify seismic signals. Seven clusters are used in this study which used PCA and t-SNE scatter plot for the K-Mean clustering. Results show that the proposed methodology demonstrates effectiveness in distinguishing between common and anomalous seismic events. Visualization and cluster analysis confirm the interpretability and practical value of this framework. From the findings, this study offers promising basis for anomaly detection and routine monitoring system with future works aimed at improving clustering techniques.
Muhammad Faizul Hadi Abu Kasim, Fazliyana ‘Izzati Za’abar, Mohd Norzaliman Mohd Zain , Norhana Arsad and Mohd Hadri Hafiz Mokhtar*
This study investigates the comparative performance of filtered and direct RGB LED illumination in confocal microscopy for biological imaging. Rotifera whole-mount samples were imaged under both illumination modes, and image quality was assessed using signal-to-noise ratio (SNR) and contrast-to- noise ratio (CNR) metrics. The highest SNR was recorded under filtered green LED illumination, whereas the highest CNR was achieved with direct red LED light. These results indicate that filtered RGB illumination enhances overall image uniformity, while direct RGB lighting more effectively accentuates structural contrast, depending on the specific imaging objective.
Nur Aina Athirah Mohd Nizar, Juliza Jamaludin*, Marinah Othman
Water turbidity is a critical parameter for assessing water quality, conventionally measured using turbidimeters that rely on nephelometric light scattering. While effective, these instruments are constrained to labor-intensive sampling, limiting spatial and delayed data analysis. This paper explores the potential of LiDAR which a photonics-based ranging technology as an alternative method for turbidity assessment. Both turbidimeters and LiDAR operate on light-particle interaction principles. In this research, a compact TFmini-S LiDAR sensor was used in a controlled laboratory setup to observe signal strength changes in relation to turbidity levels measured by a conventional turbidimeter. Though limited in range, the sensor will be use to demonstrate a relationship between signal attenuation and turbidity. These results will provide foundational support for the future use of LiDAR in scalable, noncontact, real-time turbidity monitoring. The study invites further exploration into adapting LiDAR for broader environmental water quality applications.
Mohd Narizee Mohd Nasir, Zulfadzli Yusoff*
Tapered optical fibre evanescent light wave polarisation control is demonstrated with the utilisation of free-space optics polarised resolved set-up. TE- and TM-polarised lasing light discrimination of > 20 dB could be achieved with the proposed experimental setup and with tapered optical fibre of 2 μm waist diameter. Investigation on the performance of the proposed tapered optical fibre with whispering gallery mode (WGM) optical microresonators show distinguishable TE and TM group-mode families with high Q-factor and sharp wavelength dip contrast. The proposed setup is beneficial for photonics applications such as optical sensing and quantum physics where the polarisation state of light must be established.
Naimah Mat Isa, Muhammad Razin Aiman Rizal, Aziati Husna Awang and Norhafizah Burham*
A two-dimensional transition-metal dichalcogenide material, such as tungsten disulfide (WS2), can be used to enhance the sensitivity of certain sensing applications. The impact of WS2 coating on tapered region microfiber (MF) for relative humidity (RH) sensing applications was examined in this work. The typical single-mode fiber (SMF) was tapered using the flame brushing technique to achieve a microfiber with a waist diameter of approximately 3 µm. The drop-casting process, a simple deposition technique, was then used to coat the microfiber in WS2. Depositing WS2 onto the tapered zone resulted in high humidity sensor sensitivity because the MF had a strong evanescent field that enabled quick near-field interaction between the directed light and the environment. To demonstrate repeatability and sensor stability, the experiments were repeated three times to quantify the average transmitted power. Different relative humidity (%RH) concentrations were evaluated using multiple microfiber (MF) samples to ensure repeatability. Additionally, at room temperature and in the %RH range of 40% to 60% RH, the performances of coated and uncoated microfibers were examined. Thus, microfiber coated with WS2 enhances the evanescent field effect in optical fiber humidity sensors.
Marinah Othman*, Nuraini Mohd Faizun @ Saring Cisarua, Mardhiah Nashahar, M.I.S. Mohammad Hilmy, Juliza Jamaludin, Khairul Nabilah Zainul Ariffin, Nur Najahatul Huda Saris
This paper presents a numerical study of a single-mode fiber (SMF) based surface plasmon resonance (SPR) sensor, intended for air contaminant detection. Utilizing the finite element method (FEM) in COMSOL, the sensor’s optical performance is evaluated by varying the gold coating thickness. Results demonstrate that thinner coatings yield stronger field enhancement, which is beneficial for sensitive detection applications. The findings offer insights into sensor design optimization prior to experimental implementation.
Marinah Othman*, M.I.S. Mohammad Hilmy, M. F. Mohd Fadhir, Nuraini Mohd Faizun @ Saring Cisarua, Juliza Jamaludin, Khairul Nabilah Zainul Ariffin, Nur Najahatul Huda Saris
This paper presents a dual-side polished photonic crystal fiber (PCF) designed for surface plasmon resonance (SPR) sensing. The sensor leverages a gold layer deposited on the PCF surface to excite surface plasmons, enabling highly sensitive detection of changes in the surrounding refractive index. Numerical simulations using COMSOL Multiphysics were performed to analyze the sensor's performance as a function of pitch distance, ranging from 3.0 µm to 4.0 µm. The analysis focuses on the mode characteristics and electric field distribution within the sensor. The simulation results demonstrate the influence of the PCF pitch on the sensor's optical properties. Optimal performance is achieved at a pitch of 3.0 µm, where mode confinement and electric field localization at the gold interface are strongest, enhancing surface plasmon resonance effects crucial for sensing applications.
Muhammad Hasif Bin Mahazir*, Syamsuri Bin Yaakob , Mahfida Amjad
The increasing demand for high-speed, flexible, and reliable wireless communication has driven the convergence of radio frequency (RF) and optical fiber technologies. As network traffic surges, issues like congestion and server overload become more critical. Grand View Research [1] projected that data center traffic would reach 9,965 exabytes by 2020, up from 4,515 exabytes in 2015. Additionally, SDN-based data center traffic was expected to rise from over 58% to more than 75% by 2020 [2]. Radio over Fiber (RoF) systems transmit RF signals via optical fiber, merging the high bandwidth and low attenuation of fiber optics with the mobility of wireless systems. This makes RoF essential for 5G, IoT, and smart healthcare applications [3]. Commonly used in fronthaul links, RoF connects base stations with centralized units [4]. A key challenge in RoF systems is load balancing distributing traffic efficiently across components like Remote Radio Heads (RRHs) and optical links to improve QoS, optimize resources, and maximize throughput [5]. Efficient resource allocation of bandwidth, memory, and processing power enables balanced loads, resulting in higher throughput and lower latency.
Liyana Shatar and Fariza Hanim Suhailin*
This study presents a label-free surface-enhanced Raman spectroscopy (SERS) aptasensor for the sensitive and selective detection of SARS-CoV-2 spike (S-) proteins of Wuhan and Omicron variants. Gold nanoparticles (Au NPs) were deposited onto hydroxylated silicon (Si) substrates and functionalized with variant-specific aptamers. The SERS aptasensor demonstrated a strong, concentration-dependent Raman response from 1 nM to 20 µM, with a sensitive and prominent peak at 1590 cm⁻¹ attributed to Au–thiolate bonding. The Omicron variant produced significantly higher SERS intensity than the Wuhan variant, suggesting enhanced surface interactions and Raman responses. Beside high sensitivity and capability for variant discrimination, a strong linear correlation between SERS intensity and protein concentration supports the potential of label-free SERS aptasensor for quantitative diagnostics of COVID-19.
Hasanain Naser Abd Ali*, Norhana Arsad, Aeriyn D. Ahmad, Nurul Izzah S. Wadi, Taj-Aldeen Naser Abdali
This study demonstrates the use of Polyaniline Boron Nitride (PANI-BN) as a saturable absorber for generating Q-switched pulses in a 1.5 µm erbium-doped fiber laser (EDFL). Stable Q-switching was achieved, the maximum pump powers from 212.1 mW, producing repetition rate 93.9 kHz and pulse width of 5.1 µs. The laser operated at 1532.2 nm. The results highlight PANI-BN's potential as an effective saturable absorber for enhancing EDFL performance across various applications. This innovation opens the door for the development of more efficient, reliable fiber laser systems with wideranging applications.
Nur Akmar Jamil, Muhammad Feidhul Hakim Fatah Yasin, Ilmi Munirah Karim, Nur Dina Mariha Mat Sidin, Hanis Yasmin Sofian, Chan Kiki, Affa Rozana Abdul Rashid, Syara Kassim, P. Susthitha Menon*
Surface wettability, measured via water contact angle (WCA) assessments, is an essential parameter in evaluating sensor surfaces' characteristics in plasmonic biosensing, particularly in Kretschmann-based surface plasmon resonance (K-SPR). This study examines the influence of heptylamine plasma polymerization parameters on WCA measurement and correlates these surface alterations with the biosensor sensitivity. The results showed that increasing plasma deposition power from 10 W to 80 W increased WCA from 58° to 82°, transitioning the surface from hydrophilic to hydrophobic. At an optimal power of 30 W, the surface exhibited a WCA of 61.24° and a refractive index of sensitivity (RIS) of 60°/RIU. The correlation coefficient (R² = 0.82) between plasma power and WCA confirms that controlled plasma treatment improves surface hydrophilicity and enables effective SPR based glucose detection.
Woan Wen Tan*, Naveen Palanichamy, C. Palanichamy
Two-dimensional (2D) materials are emerging in photonics due to their atomic-scale thick nature, strong interaction with light, and diverse electronic characteristics. This review explores the use of 2D materials like graphene, TMDs, BP, and hBN, focusing on their roles in high-speed modulation, photodetectors, and creating flexible, adjustable light sources. We compare their optical properties and examine their suitability for advanced photonic technologies. Material synthesis, such as wafer-scale growth and van der Waals stacking, have significantly improved their compatibility with integrated photonic platforms. However, there are critical challenges that need to deal with, such scalability, environmental stability, and CMOS compatibility. Material encapsulation techniques, producing largearea growth methods, and interface engineering are being actively pursued to overcome these limitations. This review summarizes current progress and ongoing challenges in the field.