Sharafat Ali

Bio: Sharafat Ali is an academic researcher from Massey University. The author has contributed to research in topics: Photonic-crystal fiber & Dispersion-shifted fiber. The author has an hindex of 8, co-authored 30 publications receiving 235 citations. Previous affiliations of Sharafat Ali include Universiti Malaysia Perlis & Rajshahi University of Engineering & Technology.

A Highly Sensitive Gold-Coated Photonic Crystal Fiber Biosensor Based on Surface Plasmon Resonance

Abstract: In this paper, we numerically demonstrate a two-layer circular lattice photonic crystal fiber (PCF) biosensor based on the principle of surface plasmon resonance (SPR). The finite element method (FEM) with circular perfectly matched layer (PML) boundary condition is applied to evaluate the performance of the proposed sensor. A thin gold layer is deposited outside the PCF structure, which acts as the plasmonic material for this design. The sensing layer (analyte) is implemented in the outermost layer, which permits easy and more practical fabrication process compared to analyte is put inside the air holes. It is demonstrated that, at gold layer thickness of 40 nm, the proposed sensor shows maximum sensitivity of 2200 nm/RIU using the wavelength interrogation method in the sensing range between 1.33–1.36. Besides, using an amplitude interrogation method, a maximum sensitivity of 266 RIU−1 and a maximum sensor resolution of 3.75 × 10−5 RIU are obtained. We also discuss how phase matching points are varied with different fiber parameters. Owing to high sensitivity and simple design, the proposed sensor may find important applications in biochemical and biological analyte detection.

Low Cost Sensor With IoT LoRaWAN Connectivity and Machine Learning-Based Calibration for Air Pollution Monitoring

Abstract: Air pollution poses significant risk to environment and health. Air quality monitoring stations are often confined to a small number of locations due to the high cost of the monitoring equipment. They provide a low fidelity picture of the air quality in the city; local variations are overlooked. However, recent developments in low-cost sensor technology and wireless communication systems like Internet of Things (IoT) provide an opportunity to use arrayed sensor networks to measure air pollution, in real time, at a large number of locations. This article reports the development of a novel low-cost sensor node that utilizes cost-effective electrochemical sensors to measure carbon monoxide (CO) and nitrogen dioxide (NO2) concentrations and an infrared sensor to measure particulate matter (PM) levels. The node can be powered by either solar-recharged battery or mains supply. It is capable of long-range, low power communication over public or private long-range wide area network (LoRaWAN) IoT network and short-range high data rate communication over Wi-Fi. The developed sensor nodes were co-located with an accurate reference CO sensor for field calibration. The low-cost sensors’ data, with offset and gain calibration, show good correlation with the data collected from the reference sensor. Multiple linear regression (MLR)-based temperature and humidity correction results in mean absolute percentage error (MAPE) of 48.71% and $R^{2}$ of 0.607 relative to the reference sensor’s data. Artificial neural network (ANN)-based calibration shows the potential for significant further improvement with MAPE of 38.89% and $R^{2}$ of 0.78 for leave-one-out cross-validation.

Modelling and simulation of a porous core photonic crystal fibre for terahertz wave propagation

Abstract: A porous core photonic crystal fibre based on conventional hexagonal lattice cladding is proposed for propagating terahertz radiation. The structure is designed and theoretically investigated using full vectorial finite element method. Simulation results show that at 300 µm core diameter, with a high porosity of 85%, and an operating frequency of 1.3 THz, the proposed fibre reduces the bulk absorption loss of cyclic olefin copolymer (TOPAS) by about 81%, which corresponds to an ultra-low effective material loss value of 0.039 cm−1. Furthermore, the proposed fibre shows near zero dispersion coefficient of 0.47 ps/THz/cm with an extremely small variation of 0.05 over a broad 1.3 THz bandwidth; with confinement and bending losses investigated and found to be negligibly low. It is anticipated that the proposed waveguide can potentially be used for short range transmission of terahertz radiation in the communication window.

Ultra-flat low material loss porous core THz waveguide with near zero flat dispersion

Abstract: A near zero dispersion flattened porous core photonic crystal fibre having ultra-flat low material loss suitable for terahertz (THz) transmission is represented. A novel type of geometrical structure of air hole position has been proposed in this design. Numerical analysis exhibits effective material loss (EML) of 0.03746 cm -1 at 1.0 THz operating frequency and a flat EML of 0.0398 cm -1 from 1.5 to 5.0 THz with absolute EML coefficient of ±0.000416 cm -1 . The proposed waveguide shows near zero flat dispersion of 0.4 ± 0.042 ps/THz/cm in the frequency range from 1.25 to 5.0 THz.

Ultra-high birefringent and dispersion-flattened low loss single-mode terahertz wave guiding

Abstract: This study proposes a dielectric terahertz (THz) porous core fibre with ultra-high birefringence and near zero dispersion-flattened properties The finite element method is used to design and analyse properties of the proposed THz fibre The proposed porous core crystal fibre has a triangular lattice with microstructured circular air holes in the outer cladding and elliptical air holes in the core The design exhibits a high birefringence of 7 × 10−2 and a low effective material loss of 01 cm−1 at the operating frequency of f = 1 THz It also shows nearly zero flattened dispersion with an absolute dispersion variation of ±005 ps/THz/cm in the frequency range of 13 to 22 THz Power fraction and confinement loss are also reported in this study The proposed THz porous fibre is deemed suitable for polarisation-maintaining THz wave guidance

Spiral Photonic Crystal Fiber-Based Dual-Polarized Surface Plasmon Resonance Biosensor

Abstract: We numerically demonstrate a surface plasmon resonance biosensor-based on dual-polarized spiral photonic crystal fiber (PCF). Chemically stable gold material is used as the active plasmonic material, which is placed on the outer layer of the PCF to facilitate practical fabrication. Finite-element method-based numerical investigations show that the proposed biosensor shows maximum wavelength sensitivity of 4600 and 4300 nm/RIU in ${x}$ - and ${y}$ -polarized modes at an analyte refractive index of 1.37. Moreover, for analyte refractive index ranging from 1.33 to 1.38, maximum amplitude sensitivities of 371.5 RIU−1 and 420.4 RIU−1 are obtained in ${x}$ - and ${y}$ -polarized modes, respectively. In addition, the effects of changing pitch, different air hole diameter of the PCF and thickness of the gold layer on the sensing performance are also investigated. Owing to high sensitivity, improved sensing resolution and appropriate linearity characteristics, the proposed dual-polarized spiral PCF can be implemented for the detection of biological analytes, organic chemicals, biomolecules, and other unknown analytes.

Gold-coated photonic crystal fiber biosensor based on surface plasmon resonance: Design and analysis

Abstract: The particularly sensitive circular lattice Photonic Crystal Fiber (PCF) based Surface Plasmon Resonance (SPR) sensor is proposed to gain high sensitivity for the detection of unknown analytes. In this model, two-layer PCF based on the SPR has been designed. A plasmonic chemically inactive material gold (Au) with thickness 35 nm is used to the outside of the PCF structure which exhibits negative real permittivity. A circular perfectly match layer (PML) outside the structure is applied to evaluate the performance of the sensor. The raised design has consisted of symmetric air-hole. Three small air-holes are used in second layer and center which help us to produce more evanescent field. Using the wavelength interrogation method the proposed model shows the maximum wavelength sensitivity of 9000 nm/RIU (Refractive Index Unit) and using the amplitude interrogation method it shows the maximum amplitude sensitivity of 318 RIU−1 with maximum sensor resolution 1.11 × 10−5 in the sensing range among analyte 1.34–1.37. Here the proposed model is investigated how phase matching points are varied with changing parameters as like diameter, PML, thickness of gold (Au), sensing layer and pitch. The obtained result reveals that the proposed model may be used in biochemical and biological analyte detection to find out the important application.

Plasmonic Biosensor With Gold and Titanium Dioxide Immobilized on Photonic Crystal Fiber for Blood Composition Detection

Abstract: This paper proposes a photonic crystal fiber (PCF) based plasmonic biosensor for the detection of various blood compositions like red blood cells (RBCs), hemoglobin (HB), white blood cells (WBCs), plasma, and water. The finite element method (FEM) has been used to simulate and quantitatively evaluate this biosensor. The gold and titanium dioxide coated PCF operates on the surface plasmon resonance (SPR) theory, where the gold layer acts as a plasmonic material, and the titanium dioxide layer improves adhesion between the gold layer and the PCF surface. SPR occurs at the interface between gold and the sensing channel, when the core propagation mode is coupled with the surface plasmon polariton (SPP) mode in the vicinity of the phase-matching point. Due to the occurrence of SPR, the loss peak is noticed in the core propagation mode, and this loss peak is extremely sensitive to the various blood compositions that each have their unique refractive index (RI) poured into the sensing channel of the PCF. The proposed biosensor has maximum wavelength sensitivity of 12400 nm/RIU. However, the maximum amplitude sensitivity is −574.3 RIU−1. Furthermore, with the maximum detection limit of 0.02, the refractive index resolution varies from $8.06\times {10}^{-6} {\mathrm {RIU}}$ to $5.0\times {10}^{-5} {\mathrm {RIU}}$ . As a result, it is safe to say that this biosensor will work admirably in terms of detecting blood compositions. Thus, the proposed biosensor will explore the broad realms of medical diagnostics.

Recent advances in plasmonic sensor-based fiber optic probes for biological applications

Abstract: The survey focuses on the most significant contributions in the field of fiber optic plasmonic sensors (FOPS) in recent years. FOPSs are plasmonic sensor-based fiber optic probes that use an optical field to measure the biological agents. Owing to their high sensitivity, high resolution, and low cost, FOPS turn out to be potential alternatives to conventional biological fiber optic sensors. FOPS use optical transduction mechanisms to enhance sensitivity and resolution. The optical transduction mechanisms of FOPS with different geometrical structures and the photonic properties of the geometries are discussed in detail. The studies of optical properties with a combination of suitable materials for testing the biosamples allow for diagnosing diseases in the medical field.