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Recent Submissions

  • Digital E. coli Counter: A Microfluidics and Computer Vision-Based DNAzyme Method for the Isolation and Specific Detection of E. coli from Water Samples

    Rauf, Sakandar; Tashkandi, Nouran Abdulatif; De Oliveira Filho, José Ilton; Oviedo-Osornio, Claudia Iluhí; Danish, Muhammad S.; Hong, Pei-Ying; Salama, Khaled N. (Biosensors, MDPI AG, 2022-01-10) [Article]
    Biological water contamination detection-based assays are essential to test water quality; however, these assays are prone to false-positive results and inaccuracies, are time-consuming, and use complicated procedures to test large water samples. Herein, we show a simple detection and counting method for E. coli in the water samples involving a combination of DNAzyme sensor, microfluidics, and computer vision strategies. We first isolated E. coli into individual droplets containing a DNAzyme mixture using droplet microfluidics. Upon bacterial cell lysis by heating, the DNAzyme mixture reacted with a particular substrate present in the crude intracellular material (CIM) of E. coli. This event triggers the dissociation of the fluorophore-quencher pair present in the DNAzyme mixture leading to a fluorescence signal, indicating the presence of E. coli in the droplets. We developed an algorithm using computer vision to analyze the fluorescent droplets containing E. coli in the presence of non-fluorescent droplets. The algorithm can detect and count fluorescent droplets representing the number of E. coli present in the sample. Finally, we show that the developed method is highly specific to detect and count E. coli in the presence of other bacteria present in the water sample.
  • 14 GHz Schottky Diodes using a p -Doped Organic Polymer

    Loganathan, Kalaivanan; Scaccabarozzi, Alberto D.; Faber, Hendrik; Ferrari, Federico; Bizak, Zhanibek; Yengel, Emre; Naphade, Dipti R.; Gedda, Murali; He, Qiao; Solomeshch, Olga; Adilbekova, Begimai; Yarali, Emre; Tsetseris, Leonidas; Salama, Khaled N.; Heeney, Martin; Tessler, Nir; Anthopoulos, Thomas D. (Advanced Materials, Wiley, 2022-01-06) [Article]
    The low carrier mobility of organic semiconductors and the high parasitic resistance and capacitance often encountered in conventional organic Schottky diodes, hinder their deployment in emerging radio frequency (RF) electronics. Here we overcome these limitations by combining self-aligned asymmetric nanogap electrodes (∼25 nm) produced by adhesion-lithography, with a high mobility organic semiconductor and demonstrate RF Schottky diodes able to operate in the 5G frequency spectrum. We used C<sub>16</sub> IDT-BT, as the high hole mobility polymer, and studied the impact of p-doping on the diode performance. Pristine C<sub>16</sub> IDT-BT-based diodes exhibit maximum intrinsic and extrinsic cutoff frequencies (f<sub>C</sub> ) of >100 and 6 GHz, respectively. This extraordinary performance is attributed primarily to the planar nature of the nanogap channel and the diode's small junction capacitance (< 2 pF). Doping of C<sub>16</sub> IDT-BT with the molecular p-dopant C<sub>60</sub> F<sub>48</sub> , improves the diode's performance further by reducing the series resistance resulting to intrinsic and extrinsic f<sub>C</sub> of >100 and ∼14 GHz respectively, while the DC output voltage of a RF rectifier circuit increases by a tenfold. Our work highlights the importance of the planar nanogap architecture and paves the way for the use of organic Schottky diodes in large-area radio frequency electronics of the future. This article is protected by copyright. All rights reserved.
  • Optically Transparent and Flexible Radio Frequency Electronics through Printing Technologies

    Li, Weiwei; Akhter, Zubair; Vaseem, Mohammad; Shamim, Atif (Advanced Materials Technologies, Wiley, 2022-01-05) [Article]
    With the advent of the Internet of things, 5G wireless communication, and smart city applications, demand for a new form of radio frequency (RF) electronics has risen, one that can be mounted or integrated on non-conformal objects, is mass manufacturable at lower costs, and is optically transparent to maintain the aesthetics of the environment where deployed. This new breed of electronics can be realized through printing technologies, which are capable of manufacturing diverse designs on flexible substrates via large-scale and high-volume printing techniques at lower costs. However, the major challenge for printed electronics is the preparation of conductive inks with performance comparable to their bulk metal counterparts. This review summarizes the recent developments in printable transparent and conductive materials (TCMs), inks, and methods for optically transparent RF passives. In addition, techniques to enhance the conductivity of the TCMs are presented. Moreover, it covers several design examples of optically transparent RF passives, such as antennas, microwave absorbers, and frequency selective surfaces. Furthermore, many challenges and potential solutions are discussed in terms of the TCMs, inks, and printing technologies needed for the realization of such designs. Finally, some future trends in the area of transparent RF electronics and PE are discussed.
  • A flexible capacitive photoreceptor for the biomimetic retina.

    Vijjapu, Mani Teja; Fouda, Mohamed E.; Agambayev, Agamyrat; Kang, Chun Hong; Lin, Chun-Ho; Ooi, Boon S.; He, Jr-Hau; Eltawil, Ahmed; Salama, Khaled N. (Light: Science & Applications, Springer Science and Business Media LLC, 2022-01-02) [Article]
    Neuromorphic vision sensors have been extremely beneficial in developing energy-efficient intelligent systems for robotics and privacy-preserving security applications. There is a dire need for devices to mimic the retina's photoreceptors that encode the light illumination into a sequence of spikes to develop such sensors. Herein, we develop a hybrid perovskite-based flexible photoreceptor whose capacitance changes proportionally to the light intensity mimicking the retina's rod cells, paving the way for developing an efficient artificial retina network. The proposed device constitutes a hybrid nanocomposite of perovskites (methyl-ammonium lead bromide) and the ferroelectric terpolymer (polyvinylidene fluoride trifluoroethylene-chlorofluoroethylene). A metal-insulator-metal type capacitor with the prepared composite exhibits the unique and photosensitive capacitive behavior at various light intensities in the visible light spectrum. The proposed photoreceptor mimics the spectral sensitivity curve of human photopic vision. The hybrid nanocomposite is stable in ambient air for 129 weeks, with no observable degradation of the composite due to the encapsulation of hybrid perovskites in the hydrophobic polymer. The functionality of the proposed photoreceptor to recognize handwritten digits (MNIST) dataset using an unsupervised trained spiking neural network with 72.05% recognition accuracy is demonstrated. This demonstration proves the potential of the proposed sensor for neuromorphic vision applications.
  • Ultra-Thin Artificial Magnetic Conductor for Gain-Enhancement of Antenna-on-Chip

    Yu, Yiyang; Akhter, Zubair; Shamim, Atif (IEEE Transactions on Antennas and Propagation, IEEE, 2022) [Article]
    System-on-Chip (SoC) has become an attractive solution to achieve highly integrated wireless systems. However, the Antenna-on-Chip (AoC) suffers from poor radiation due to the lossy silicon substrate in standard CMOS processes. Artificial Magnetic Conductors (AMC) with the ground plane above the silicon can enhance the radiation, however, fitting the AMC completely in the thin stack-up (~10-15 μm) is extremely challenging, particularly for frequencies below 100 GHz. In this paper, Metallic Posts (MP) and Embedded Guiding Structures (EGS) have been investigated to reduce the AMC thickness by employing the available vias and metal layers in the stack-up. An in-house CMOS-compatible process has been used to realize the AoC, where typical low-conductivity adhesion layers have been avoided to reduce the undesired losses by using the surface roughness in a unique fashion. With MP and EGS approaches, AMC thickness can be reduced by 33% and 41% respectively. The AMC with EGS fits within an oxide of a thickness of 16 μm. A monopole antenna, backed by this AMC, demonstrates a gain of 5.85 dBi and radiation efficiency of 57% at 94 GHz, bettering the gain and radiation efficiency by 9.15 dB and 42% respectively as compared to the case without AMC.
  • 'All In One' SARS-CoV-2 variant recognition platform: Machine learning-enabled point of care diagnostics

    Beduk, Duygu; Ilton de Oliveira Filho, José; Beduk, Tutku; Harmanci, Duygu; Zihnioglu, Figen; Cicek, Candan; Sertoz, Ruchan; Arda, Bilgin; Goksel, Tuncay; Turhan, Kutsal; Salama, Khaled N.; Timur, Suna (Biosensors and Bioelectronics: X, Elsevier BV, 2022-01) [Article]
    Point of care (PoC) devices are highly demanding to control current pandemic, originated from severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2). Though nucleic acid-based methods such as RT-PCR are widely available, they require sample preparation and long processing time. PoC diagnostic devices provide relatively faster and stable results. However they require further investigation to provide high accuracy and be adaptable for the new variants. In this study, laser-scribed graphene (LSG) sensors are coupled with gold nanoparticles (AuNPs) as stable promising biosensing platforms. Angiotensin Converting Enzyme 2 (ACE2), an enzymatic receptor, is chosen to be the biorecognition unit due to its high binding affinity towards spike proteins as a key-lock model. The sensor was integrated to a homemade and portable potentistat device, wirelessly connected to a smartphone having a customized application for easy operation. LODs of 5.14 and 2.09 ng/mL was achieved for S1 and S2 protein in the linear range of 1.0–200 ng/mL, respectively. Clinical study has been conducted with nasopharyngeal swabs from 63 patients having alpha (B.1.1.7), beta (B.1.351), delta (B.1.617.2) variants, patients without mutation and negative patients. A machine learning model was developed with accuracy of 99.37% for the identification of the SARS-Cov-2 variants under 1 min. With the increasing need for rapid and improved disease diagnosis and monitoring, the PoC platform proved its potential for real time monitoring by providing accurate and fast variant identification without any expertise and pre sample preparation, which is exactly what societies need in this time of pandemic.
  • A Low-Profile and High Aperture Efficiency Hexagonal Circularly Polarized Microstrip Antenna Array

    Liao, Hanguang; Shamim, Atif (IEEE Antennas and Wireless Propagation Letters, IEEE, 2022) [Article]
    In this letter, a high aperture efficiency (AP), right hand circularly polarized (RHCP), sequentially rotated hexagonal microstrip antenna array, working at GPS L1 band, is proposed. The proposed antenna design is placed on the hexagonal top of a floating sensor node for ocean and marine monitoring applications. To use the hexagonal area effectively and maximize the AP, CP microstrip antenna elements have been distributed centrosymmetric about the origin on the hexagonal substrate. Typically, the AP is enhanced by using thicker substrates, particularly with air gaps. Here, we show a high AP on a very low-profile substrate (0.011 for the lowest operating frequency) by properly choosing the distance of the antenna elements from the center of the array. The proposed design, based on H-shaped aperture-coupled circular patches, demonstrates a measured gain of 12.4 dBi and an AP of 101%, which is one of the highest reported AP for one of the lowest profile sequentially rotational array.
  • Channel Characterization of IRS-based Visible Light Communication Systems

    Abdelhady, Amr Mohamed Abdelaziz; Amin, Osama; Salem, Ahmed Sultan; Alouini, Mohamed-Slim; Shihada, Basem (Accepted by IEEE Transactions on Communications, Accepted by IEEE, 2022) [Article]
    This paper studies the temporal characteristics of the intelligent reflecting surface (IRS)-based visible light communication (VLC) channel using radiometric concepts. Throughout this study, we account for the delays experienced by the transmitted power along the continuum of paths originating at the source, passing through the IRS, reaching the detector. Then, we derive the impulse response of multi-element phase-tunable metasurface and orientation-tunable mirror array-based reflector setups for a general setting of source, reflector, and detector dimensions and relative positions. In addition, we derive simpler expressions for the two special cases, namely, the point source and the large-source small-reflector. Moreover, we present the exact expression for the delay spread and derive lower, upper bounds and asymptotic expressions when the number of reflecting elements increases for both reflector types. Finally, we study the impact of several system parameters on the temporal characterization of the two IRS-based VLC systems.
  • Implementation of a dpu-based intelligent thermal imaging hardware accelerator on fpga

    Hussein, Abdelrahman S.; Anwar, Ahmed; Fahmy, Yasmine; Mostafa, Hassan; Salama, Khaled N.; Kafafy, Mai (Electronics (Switzerland), MDPI AG, 2021-12-29) [Article]
    Thermal imaging has many applications that all leverage from the heat map that can be constructed using this type of imaging. It can be used in Internet of Things (IoT) applications to detect the features of surroundings. In such a case, Deep Neural Networks (DNNs) can be used to carry out many visual analysis tasks which can provide the system with the capacity to make decisions. However, due to their huge computational cost, such networks are recommended to exploit custom hardware platforms to accelerate their inference as well as reduce the overall energy consumption of the system. In this work, an energy adaptive system is proposed, which can intelligently configure itself based on the battery energy level. Besides achieving a maximum speed increase that equals 6.38X, the proposed system achieves significant energy that is reduced by 97.81% compared to a conventional general-purpose CPU.
  • Compact scintillating-fiber/450-nm-laser transceiver for full-duplex underwater wireless optical communication system under turbulence

    Guo, Yujian; Kong, Meiwei; Sait, Mohammed; Marie, Sohailh; Alkhazragi, Omar; Ng, Tien Khee; Ooi, Boon S. (Optics Express, The Optical Society, 2021-12-20) [Article]
    The growing need for ocean monitoring and exploration has boosted underwater wireless optical communication (UWOC) technology. To solve the challenges of pointing, acquisition, and tracking (PAT) in UWOC technology, herein, we propose a 450-nm-laser/scintillating-fiber-based full-duplex (FD)-UWOC system for omnidirectional signal detection in real scenarios. The FD-UWOC system has a −3 dB bandwidth of 67 MHz with a low self-interference level of −44.59 dB. It can achieve a 250-Mbit/s data rate with on–off keying modulation scheme. The system’s robustness was validated by operating over 1.5-m underwater channel with air-bubble-, temperature-, salinity-, turbidity-, and mobility-induced turbulence with a low outage probability. Under air-bubble-induced turbulence, the highest outage probability was 28%. With temperature-, salinity-, and turbidity-induced turbulence, the system performed adequately, showing a highest outage probability of 0%, 3%, and 4%, respectively. In mobile cases, the highest outage probability of the FD-UWOC system was 14%, compared to an outage probability of 100% without utilizing the fluorescent optical antenna. To further validate its robustness, a deployment test was conducted in an outdoor diving pool. The system achieved a 250-Mbit/s data rate over a 7.5-m working distance in the stationary case and a 1-m working range in the mobile case with a 0% outage probability. The scintillating-fiber-based detector can be employed in UWOC systems and would help relieve PAT issues.
  • Field Assessment of Camera Based Drilling Dynamics

    Koulidis, Alexis; Abdullatif, Mohamed; Abdel-Kader, Ahmed Galal; Ayachi, Mohammed Ilies; Ahmed, Shehab; Gooneratne, Chinthaka; Magana-Mora, Arturo; Affleck, Mike; Alsheikh, Mohammed (SPE, 2021-12-15) [Conference Paper]
    Surface data measurement and analysis are an established mean of detecting drillstring low-frequency torsional vibration or stick-slip. The industry has also developed models that link surface torque and downhole drill bit rotational speed. Cameras provide an alternative noninvasive approach to existing wired/wireless sensors used to gather such surface data. The results of a preliminary field assessment of drilling dynamics utilizing camera-based drillstring monitoring are presented in this work. Detection and timing of events from the video are performed using computer vision techniques and object detection algorithms. A real-time interest point tracker utilizing homography estimation and sparse optical flow point tracking is deployed. We use a fully convolutional deep neural network trained to detect interest points and compute their accompanying descriptors. The detected points and descriptors are matched across video sequences and used for drillstring rotation detection and speed estimation. When the drillstring's vibration is invisible to the naked eye, the point tracking algorithm is preceded with a motion amplification function based on another deep convolutional neural network. We have clearly demonstrated the potential of camera-based noninvasive approaches to surface drillstring dynamics data acquisition and analysis. Through the application of real-time object detection algorithms on rig video feed, surface events were detected and timed. We were also able to estimate drillstring rotary speed and motion profile. Torsional drillstring modes can be identified and correlated with drilling parameters and bottomhole assembly design. A novel vibration array sensing approach based on a multi-point tracking algorithm is also proposed. A vibration threshold setting was utilized to enable an additional motion amplification function providing seamless assessment for multi-scale vibration measurement. Cameras were typically devices to acquire images/videos for offline automated assessment (recently) or online manual monitoring (mainly), this work has shown how fog/edge computing makes it possible for these cameras to be "conscious" and "intelligent," hence play a critical role in automation/digitalization of drilling rigs. We showcase their preliminary application as drilling dynamics and rig operations sensors in this work. Cameras are an ideal sensor for a drilling environment since they can be installed anywhere on a rig to perform large-scale live video analytics on drilling processes.
  • Internet of Things IoT Edge Computer Vision Systems on Drilling Rigs

    Alsheikh, Mohammed; Gooneratne, Chinthaka; Magana-Mora, Arturo; Ibrahim, Mohamad; Affleck, Mike; Contreras, William; Zhan, Guodong David; Jamea, Musab Al; Umairin, Isa Al; Zaghary, Ahmed; Ayachi, Mohammed Ilies; Abdelkader, Ahmed Galal; Ahmed, Shehab; Makowski, Greg; Kapoor, Hitesh (SPE, 2021-12-15) [Conference Paper]
    This study focuses on the design and infrastructure development of Internet-of-Things (IoT) edge platforms on drilling rigs and the testing of pilot IoT-Edge Computer Vision Systems (ECVS) for the optimization of drilling processes. The pilot technology presented in this study, Well Control Space Out System (WC-SOS), reduces the risks associated with hydrocarbon release during drilling by significantly increasing the success and time response for shut-in a well. Current shut-in methods that require manual steps are prone to errors and may take minutes to perform, which is enough time for an irreversible escalation in the well control incident. Consequently, the WC-SOS enables the drilling rig crew to shut-in a well in seconds. The IoT-ECVS deployed for the WC-SOS can be seamlessly expanded to analyze drillstring dynamics and drilling fluid cuttings/solids/flow analysis at the shale shakers in real-time. When IoT-ECVSs communicate with each other, their value is multiplied, which makes interoperability essential for maximizing benefits in drilling operations.
  • Micromechanics of Drilling: A Laboratory Investigation of Formation Evaluation at the Bit

    Koulidis, Alexis; Mohamed, Fahd Mohamed; Ahmed, Shehab (SPE, 2021-12-15) [Conference Paper]
    Challenging drilling applications and low oil prices have created a new emphasis on innovation in the industry. This research investigates the value of drill bit based force sensing at the rock-cutter interface. For this purpose, a laboratory-based mini-rig has been built in order to recreate a scaled drilling process. The work aims to build a better understanding of the collected force and torque data despite the semi-continuous drilling process. This data is then used to estimate the formation strength. A scaled drill bit with two cutters was designed with sensors integrated into the drill bit cutter, drill string and the mini-rig structure. The mini-rig design allowed the accurate control of depth of cut by utilizing a comprehensive data acquisition and control system during the experiments. Initially, fifty-five samples were prepared with various water/gypsum ratios for a uniaxial compression test, scratch test, and for testing in the mini-rig. Prior to the mini-rig experiments, the results of the uniaxial compression and scratch tests were used as a benchmark to extract rock properties and the state of stress behavior. The experiments under atmospheric conditions revealed that the mini-rig could accurately estimate formation strength from a few rotations. The force data at the bit-rock interface was correlated with the torque measurements, and the results indicate that the tangential force has similar trends and relatively similar values. The groove created by the drill bit's rotating trajectory has a 14.45 cm circumference. This allows for a significant amount of data to be captured from a single rotation. The circular cutter geometry's influence is crucial for a continuous process since the active cutting area is continuously changing due to the pre-cut groove. The performed depth of cuts ranged from 0.1 to 1 mm in the same groove, and thus the active cutting area can be accurately calculated in real-time while conducting the experiments. Tangential and normal force data from the scratch test was analyzed in order to provide insights for correlation with the mini-rig data. The analysis shows that both tests give similar trends to the force measurements from the mini-rig. Moreover, the benchmark value of formation strength that was obtained from the uniaxial compression test was also in the same range. This illustrates the potential viability of drill bit based formation strength measurement due to the similarity between mini-rig test results and those using more classical testing practices. The experimental setup can provide a continuous cutting process that allows an accurate estimation of formation strength during a semi-continuous drilling operation with analogous application in the field. This can lead to an in-depth understanding of drilled formation properties while drilling and possibly assist in evaluating cutter wear state in-situ.
  • Application of a Drilling Simulator for Real-Time Drilling Hydraulics Training and Research

    Skenderija, Jelena; Koulidis, Alexis; Kelessidis, Vassilios; Ahmed, Shehab (SPE, 2021-12-15) [Conference Paper]
    Challenging wells require an accurate hydraulic model to achieve maximum performance for drilling applications. This work was conducted with a simulator capable of recreating the actual drilling process, including on-the-fly adjustments of the drilling parameters. The paper focuses on the predictions of the drilling simulator's pressure losses inside the drill string and across the open-hole and casing annuli applying the most common rheological models. Comparison is then made with pressure losses from field data. Drilling data of vertical and deviated wells were acquired to recreate the actual drilling environment and wellbore design. Several sections with a variety of wellbore sizes were simulated in order to observe the response of the various rheological models. The simulator allows the input of wellbore and bottom-hole assembly (BHA) sizes, formation properties, drilling parameters, and drilling fluid properties. To assess the hydraulic model's performance during drilling, the user is required to input the drilling parameters based on field data and match the penetration rate. The resulting simulator hydraulic outputs are the equivalent circulation density (ECD) and standpipe pressure (SPP). The simulator's performance was assessed using separate simulations with different rheological models and compared with actual field data. Similarities, differences, and potential improvements were then reported. During the simulation, the most critical drilling parameters are displayed, emulating real-time measured values, combined with the pore pressure, wellbore pressure, and fracture pressure graphs. The simulation results show promise for application of real-time hydraulic operations. The simulated output parameters, ECD and SPP, have similar trends and values with the values from actual field data. The simulator's performance shows excellent matching for a simple BHA, with decreasing system's accuracy as the BHA design becomes more complex, an area of future improvement. The overall approach is valid for non-Newtonian drilling fluid pressure losses. The user can observe the output parameters, and by adding a benchmark safety value, the simulator gives a warning of a potential fracture of the formation or maximum pressure at the mud pumps. Thus, by simulating the drilling process, the user can be trained for the upcoming drilling campaign and reach the target depth safely and cost-effectively during actual drilling. The simulator allows emulation of real-time hydraulic operations when drilling vertical and directional wells, albeit with a simple BHA for the latter. The user can instantly observe the output results, which allows proper action to be taken if necessary. This is a step towards real-time hydraulic operations. The results also indicate that the simulator can be used as an excellent training tool for professionals and students by creating wellbore exercises that can cover different operating scenarios.
  • Theory and Practice of Orbital Angular Momentum and Beyond

    Trichili, Abderrahmen; Cox, Mitchell A.; Perez-Garcia, Benjamin; Ooi, Boon S.; Alouini, Mohamed-Slim (Wiley, 2021-12-14) [other]
    Nearly three decades since its discovery, orbital angular momentum (OAM) has proven to be highly versatile for a wide range of applications. It is an indispensable tool in quantum optics, has made a significant impact in optical tweezing, enabled higher contrast and more detailed imaging, and offers a convenient way to harness the space degree of freedom in telecommunications. In this paper, we present a review of a wide range of applications of OAM as well as describing the creation and detection of OAM modes, with a focus on the use of OAM in communications. In addition, we detail various similar higher-order optical modes, such as vector vortex modes, and provide an introduction to the use of OAM in quantum optics, pitched for readers new to the field.
  • Visible-Light Laser Diodes and Superluminescent Diodes: Characteristics and Applications

    Alkhazragi, Omar; Holguín-Lerma, Jorge A.; Ng, Tien Khee; Ooi, Boon S. (Wiley, 2021-12-14) [Article]
    Semiconductor light-emitting technology has seen tremendous strides in recent decades and a rapidly increasing interest in it. The unique advantages and characteristics of this form of light generation include compactness, high efficiency, and reliability. With these recent advancements, light-emitting diodes (LEDs), laser diodes, and superluminescent diodes (SLDs) have become an indispensable part of our homes, factories, and research facilities. In particular, the sensitivity of the human eye to the visible wavelengths of the electromagnetic spectrum extending from 400 to 700 nm, and the optical response of many materials to such spectrum, make visible light indispensable for a plethora of applications ranging from displays for entertainment, to imaging in the medical field, to light-based atomic clocks. While LEDs are the most commonly found type of semiconductor light sources, laser diodes and SLDs are of special interest due to their higher output optical power, spectral purity, and coherence. In this tutorial, we first go over the main unique characteristics of the different types and configurations of visible-light laser diodes and SLDs and their general structures with a focus on their advantages compared to LEDs. We then discuss the applications in which these characteristics are of great interest in the fields of displays, communication, instrumentation, and photonic integrated circuits.
  • Optical Wavefront Detection: A Beginner Tutorial

    Zheng, Shuiqin; Al Ibrahim, Redha H.; Ng, Tien Khee; Ooi, Boon S. (Wiley, 2021-12-14) [Article]
    This article is designed to help readers understand some typical wavefront detection techniques and gain a preliminary understanding of wavefront detection. In this tutorial, the wavefront definition used in wavefront technology is given and we divide wavefront detection technologies into qualitative and quantitative categories. In each category, we discuss some typical systems and provide simulation results. This tutorial comes with Matlab simulation codes that readers can use to simulate mentioned wavefront detection technologies on their computers. We hope that this tutorial provides readers with all the tools needed to understand and simulate the different wavefront technologies and modify them based on their needs and interest.
  • Harvesting Electricity by Harnessing Nature: Bioelectricity, Triboelectricity, and Method of Storage

    Gopi, Chandu V.V.Muralee; Ng, Tien Khee; Ooi, Boon S. (Wiley, 2021-12-14) [Article]
    In nature, bioelectricity refers to electrical potentials and currents produced by or used within living cells, tissues, and organisms for electrolocation, predation, or protection. Electric eels can generate huge amounts of power using electric organs that are arranged in stacks of electrocytes. One critical, recent issue for electronic gadgets is that energy storage systems are incapable of offering enough energy for uninterrupted, long-running processes. This results in frequent recharging or inconvenient energy storage unit replacement. To address this challenge, inspired by bioelectricity phenomena, a unique triboelectric nanogenerator (TENG) technology has been proposed to convert small quantities of mechanical energy into electricity without an external power supply. Several advances have been made regarding TENG-based self-charging energy storage devices. To fulfill the sustainable operation requirements of the next-generation electronic devices, extensive work has been performed to integrate energy-generating TENGs with energy-storing supercapacitor devices to form self-charging power systems (SCPSs). This tutorial article focuses on the recent advances and various SCPS structural designs. In addition, various power management circuits that can be integrated with TENG devices and supercapacitors are reviewed. Finally, challenges and perspectives for future SCPS progress are discussed.
  • Localized surface plasmon resonance-enhanced solar-blind Al0.4Ga0.6N MSM photodetectors exhibiting high-temperature robustness

    Kaushik, Shuchi; Karmakar, Subhajit; Bisht, Prashant; Liao, Che-Hao; Li, Xiaohang; Varshney, Ravi; Mehta, B. R.; Singh, Rajendra (Nanotechnology, IOP Publishing, 2021-12-13) [Article]
    The appealing properties of tunable direct wide bandgap, high-temperature robustness and chemical hardness, make AlxGa1-xN a promising candidate for fabricating robust solar-blind photodetectors (PDs). In this work, we have utilized the optical phenomenon of localized surface plasmon resonance (LSPR) in metal nanoparticles (NPs) to significantly enhance the performance of solar-blind Al0.4Ga0.6N metal-semiconductor-metal (MSM) PDs that exhibit high-temperature robustness. We demonstrate that the presence of palladium (Pd) NPs leads to a remarkable enhancement by nearly 600, 300, and 462%, respectively, in the photo-to-dark current ratio (PDCR), responsivity, and specific detectivity of the Al0.4Ga0.6N PD at the wavelength of 280 nm. Using the optical power density of only 32 μWcm$^{−2}$ at −10 V, maximum values of ~3×10$^{3}$,2.7 AW$^{−1}$, and 2.4×10$^{13}$Jones are found for the PDCR, responsivity and specific detectivity, respectively. The experimental observations are supported by finite difference time domain (FDTD) simulations, which clearly indicate the presence of LSPR in Pd NPs decorated on the surface of Al0.4Ga0.6N. The mechanism behind the enhancement is investigated in detail, and is ascribed to the LSPR induced effects, namely, improved optical absorption, enhanced local electric field and LSPR sensitization effect. Moreover, the PD exhibits a stable operation up to 400 K, thereby exhibiting the high-temperature robustness desirable for commercial applications.
  • Boosted Ultraviolet Photodetection of AlGaN Quantum-Disk Nanowires via Rational Surface Passivation

    Huang, Chen; Liang, Fangzhou; Yu, Huabin; Tian, Meng; Zhang, Haochen; Ng, Tien Khee; Ooi, Boon S.; Sun, Haiding (Journal of Physics D: Applied Physics, IOP Publishing, 2021-12-09) [Article]
    Self-assembled AlGaN nanowires (NWs) are regarded as promising structures in the pursuit of ultraviolet photodetectors (UV PDs). However, AlGaN nanowire-based PDs currently suffer from degraded performance partially owing to the existence of outstanding surface-related defects/traps as a result of its large surface-to-volume-ratio feature. Here, we propose an effective passivation approach to suppress such surface states via tetramethyl ammonium hydroxide (TMAH) solution treatment. We successfully demonstrate a fabrication of UV PDs using TMAH-passivated AlGaN quantum-disk NWs and investigate their optical and electrical properties. Particularly, the dark current can be significantly reduced by an order of magnitude after surface passivation, thus leading to the improvement of photoresponsivity and detectivity. The underlying mechanism for such boost can be ascribed to the effective elimination of oxygen-related surface states on the nanowire surface. Consequently, an AlGaN nanowire UV PD with a low dark current of 6.22×10-9 A, a large responsivity of 0.95 A W-1, and a high detectivity of 6.4×1011 Jones has been achieved.

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