Hot Topics

2022-04-13
PIER
Vol. 173, 71-92, 2022
VOC Detections with Optical Spectroscopy
Yuxin Xing Gaoxuan Wang Tie Zhang Fengjiao Shen Lingshuo Meng Lihui Wang Fangmei Li Yuqi Zhu Yuhao Zheng Nan He Sailing He
Volatile organic compounds (VOCs) have received increasing attentions recently. They are important for air quality monitoring, and biomarkers for diseases diagnosis. For the gas sensor community, various detection technologies were explored not only to detect total VOCs, but also aim for sensor selectivity. Commercially available VOC sensors, such as metal oxide based or photoionization detectors, are suitable for total VOCs but lack of selectivity. With the advancement of optical spectroscopy, it provides a good solution for specific VOC detections. In this review, various spectroscopy techniques are summarised focusing on increasing sensor sensitivity and selectivity. The techniques included in the paper are, non-dispersive infrared, multi-pass cell spectroscopy, cavity enhanced absorption photoacoustic spectroscopy and Fourier transform infrared spectroscopy. Each technique has its pros and cons, which are also discussed.
VOC DETECTIONS WITH OPTICAL SPECTROSCOPY
2020-10-15
PIER
Vol. 168, 61-71, 2020
Polarization Reconfigurable Slot-Fed Cylindrical Dielectric Resonator Antenna
Mahbubeh Esmaeili Jean-Jacques Laurin
A new design for a cylindrical dielectric resonator antenna (DRA) with a capability of switching between circular, linear horizontal and linear vertical polarizations is introduced. The DRA, operating at the center frequency of 3.25 GHz, is fed by a microstrip line through two dog-bone slots. In this design, only two PIN diodes are employed as switching elements which significantly decreases the complexity of DC biasing circuits compared to existing designs. The PIN diodes are embedded in transformers connected to the feeding microstrip lines. This technique conveniently allows to make compensations for parasitic effects of the PIN diodes junction capacitors on the antenna matching bandwidth. The circular, linear horizontal and linear vertical polarizations have a bandwidth of 22%, 17% and 18%, respectively. The 3-dB axial ratio bandwidth for the circular polarization is 12%. The measured results obtained from prototyped antenna agree well with simulated results of the designed antenna system, which confirms the validity of the design process.
POLARIZATION RECONFIGURABLE SLOT-FED CYLINDRICAL DIELECTRIC RESONATOR ANTENNA
2021-03-18
PIER C
Vol. 111, 61-72, 2021
Gain Enhancement of SIW Cavity-Backed Antenna Using Dielectric Loading
Dhara Milan Patel Falguni Raval
This article presents the design and development of a low profile substrate integrated waveguide semi-circular cavity-backed antenna loaded with dielectric cylinders of glass-reinforced epoxy and Teflon. The substrate integrated waveguide semi-circular cavity-backed antenna without dielectric loading radiates at 5.8 GHz with 3.13 dB gain. The antenna is modified by putting dielectric cylinders of different materials and different sizes at the edge of a semi-circular cavity to enhance the gain of the antenna. The new antenna thus created has improved gain of 8.13 dB. All simulations are done using high frequency structure simulation software. The proposed design is fabricated on a glass-reinforced epoxy substrate with a semi-circular cavity having a size of 60 mm x 50 mm. The measured results are in good agreement with simulated ones.
GAIN ENHANCEMENT OF SIW CAVITY-BACKED ANTENNA USING DIELECTRIC LOADING
2020-12-30
PIER
Vol. 169, 59-71, 2020
A Review of Algorithms and Hardware Implementations in Electrical Impedance Tomography (Invited)
Zheng Zong Yusong Wang Zhun Wei
In recent years, electrical impedance tomography (EIT) has attracted intensive interests due to its noninvasive, ionizing radiation-free, and low-cost advantages, which is promising for both biomedical imaging and industry nondestructive tests. The purpose of this paper is to review state-of-the-art methods including both algorithms and hardwares in EIT. More specifically, for the advanced reconstruction algorithms in mainstream, we offer some insights on classification and comparison. As for the measurement equipment, the structure, configuration modes, and typical systems are reviewed. Furthermore, we discuss the limitations and challenges in EIT technique, such as low-spatial resolution and nonlinear-inversion problems, where future directions, such as solving EIT problems with deep learning, have also been addressed.
A REVIEW OF ALGORITHMS AND HARDWARE IMPLEMENTATIONS IN ELECTRICAL IMPEDANCE TOMOGRAPHY (INVITED)
2022-06-07
PIER
Vol. 174, 55-73, 2022
A Review of Multifunctional Optical Gap-Surface Plasmon Metasurfaces
Fei Ding
Gap-surface plasmon (GSP) metasurfaces that consist of metallic resonators, a middle dielectric spacer, and a back metallic reflector have become an emerging research area due to their excellent properties, such as ease of fabrication, high efficiency, and unprecedented capabilities of controlling reflected fields. In this concise review, we introduce our efforts in exploring the physical principles and fascinating applications of multifunctional GSP metasurfaces in the optical range. Starting with a typical GSP meta-atom, we present the concept and mechanism of simultaneous and independent phase and polarization control. We then overview some typical applications of GSP metasurfaces, including beam-steering, surface plasmon polariton coupling, metalenses, meta-waveplates, and dynamical metasurfaces. The review is ended with a short perspective on future developments in this area.
A REVIEW OF MULTIFUNCTIONAL OPTICAL GAP-SURFACE PLASMON METASURFACES
2022-03-09
PIER
Vol. 173, 53-69, 2022
On Fresnel-Airy Equations, Fabry-Perot Resonances and Surface Electromagnetic Waves in Arbitrary Bianisotropic Metamaterials
Maxim Durach Robert Williamson Jacob Adams Tonilynn Holtz Pooja Bhatt Rebecka Moreno Franchescia Smith
We introduce a theory of optical responses of bianisotropic layers with arbitrary effective medium parameters, which results in generalized Fresnel-Airy equations for reflection and transmission coefficients at all incidence directions and polarizations. The poles of these equations provide explicit expressions for the dispersion of Fabry-Perot resonances and surface electromatic waves in bianisotropic layers and interfaces. The existence conditions of these resonances are topologically related to the zeros of the high-k characteristic function h(k)=0 of bulk bianisotropic materials and taxonomy of bianisotropic media according to the hyperbolic topological classes [32, 33].
ON FRESNEL-AIRY EQUATIONS, FABRY-PEROT RESONANCES AND SURFACE ELECTROMAGNETIC WAVES IN ARBITRARY BIANISOTROPIC METAMATERIALS
2020-12-12
PIER
Vol. 169, 45-57, 2020
Rotman Lens Design with Wideband DRA Array
Mohammad Ranjbar Nikkhah Manish Hiranandani Ahmed A. Kishk
For rapid Rotman lens design, the symmetry plane is utilized to reduce the structure size by employing the odd and even mode characteristics. Solutions of half the structure for odd and even modes (short and open walls or electrical and magnetic walls, respectively) are much more efficient than the one-time solution for the whole structure. Then, s-parameters from both solutions are processed to obtain the s-parameters of the full lens. To support the wideband and wide scanning range, DRA array is used because of its ability to support these characteristics. Two examples are considered. The first example that employs four cylindrical DRA elements is built and measured to test the concept of terminating the dummy ports by absorbing materials instead of matching loads. This termination tremendously simplifies the structure and reduces the cost by saving the terminating connectors and the matching loads. Here, thin planar absorbing material is used on top of the microstrip lines of the dummy ports. The simulated and measured results are in good agreement. The second example utilizes 8 rectangular DRA array elements and is studied numerically.
ROTMAN LENS DESIGN WITH WIDEBAND DRA ARRAY
2022-08-09
PIER
Vol. 175, 45-79, 2022
Machine Learning-Assisted Sensing Techniques for Integrated Communications and Sensing in WLANs : Current Status and Future Directions
Siyuan Shao Min Fan Cheng Yu Yan Li Xiaodong Xu Haiming Wang
Sensing is a key basis for building an intelligent environment. Using channel state information (CSI) from the IEEE 802.11 physical layer in the wireless local access networks, the CSIbased device-free sensing technique has become very promising to the current sensing solutions because of its non-invasion of privacy, non-contact, easy deployment, and low cost. In recent years, the integrated communication and sensing (ICAS) technology has become one of the popular research topics in both wireless communications and computer areas. Given the fruitful advancements of ICAS, it is essential to review these advancements to synthesize and give previous research experiences and references to aid the development of relevant research fields and real-world applications. Motivated by this, this paper aims to provide a comprehensive survey of CSI-based sensing techniques. This study categorizes the surveyed works into model-based methods, data-based methods, and model-data hybrid-driven methods. Some important physical models and machine learning algorithms are also introduced. The sensing functions are classified into detection, estimation, and recognition according to specific application scenarios. Furthermore, future directions and challenges are discussed.
MACHINE LEARNING-ASSISTED SENSING TECHNIQUES FOR INTEGRATED COMMUNICATIONS AND SENSING IN WLANS: CURRENT STATUS AND FUTURE DIRECTIONS
2022-05-23
PIER
Vol. 174, 43-53, 2022
Comparison of Correlation Performance for Various Measurement Schemes in Quantum Bipartite Radar and Communication Systems
Rory A. Bowell Matthew J. Brandsema Ram M. Narayanan Stephen W. Howell Jonathan M. Dilger
Bipartite systems have become popular in emerging quantum radar and quantum communication systems. This paper analyzes the various correlation coefficients for different types of quantum radar measurement schemes, such as: (i) immediate detection of the idler photon events to be used in post-processing correlation with the signal photon events, (ii) immediate detection of the idler electric field to be used in post-processing correlation with the signal electric field, (iii) immediate detection of the idler quadratures to be used in post-processing correlation with the signal quadratures, and (iv) conventional analog correlation method of the optical parametric amplifier. The showcased results compare the performance of these different methodologies for various environmental scenarios. This work is important at developing the fundamentals behind quantum technologies that require covariance measurements and will permit more accurate selection of the appropriate measurement styles for individual systems.
COMPARISON OF CORRELATION PERFORMANCE FOR VARIOUS MEASUREMENT SCHEMES IN QUANTUM BIPARTITE RADAR AND COMMUNICATION SYSTEMS
2020-10-03
PIER
Vol. 168, 39-59, 2020
Fundamental Implicit FDTD Schemes for Computational Electromagnetics and Educational Mobile Apps (Invited Review)
Eng Leong Tan
This paper presents an overview and review of the fundamental implicit finite-difference time-domain (FDTD) schemes for computational electromagnetics (CEM) and educational mobile apps. The fundamental implicit FDTD schemes are unconditionally stable and feature the most concise update procedures with matrix-operator-free right-hand sides (RHS). We review the developments of fundamental implicit schemes, which are simpler and more efficient than all previous implicit schemes having RHS matrix operators. They constitute the basis of unification for many implicit schemes including classical ones, providing insights into their inter-relations along with simplifications, concise updates and efficient implementations. Based on the fundamental implicit schemes, further developments can be carried out more conveniently. Being the core CEM on mobile apps, the multiple one-dimensional (M1-D) FDTD methods are also reviewed. To simulate multiple transmission lines, stubs and coupled transmission lines efficiently, the M1-D explicit FDTD method as well as the unconditionally stable M1-D fundamental alternating direction implicit (FADI) FDTD and coupled line (CL) FDTD methods are discussed. With the unconditional stability of FADI methods, the simulations are fast-forwardable with enhanced efficiency. This is very useful for quick concept illustrations or phenomena demonstrations during interactive teaching and learning. Besides time domain, many frequency-domain methods are well-suited for further developments of useful mobile apps as well.
FUNDAMENTAL IMPLICIT FDTD SCHEMES FOR COMPUTATIONAL ELECTROMAGNETICS AND EDUCATIONAL MOBILE APPS (INVITED REVIEW)
2022-03-09
PIER
Vol. 173, 37-52, 2022
Massively Parallel Multilevel Fast Multipole Algorithm for Extremely Large-Scale Electromagnetic Simulations: a Review
Wei-Jia He Xiao-Wei Huang Ming-Lin Yang Xin-Qing Sheng
Since the first working multilevel fast multipole algorithm (MLFMA) for electromagnetic simulations was proposed by Chew's group in 1995, this algorithm has been recognized as one of the most powerful tools for numerical solutions of extremely large electromagnetic problems with complex geometries. It has been parallelized with different strategies to explore the computing power of supercomputers, increasing the size of solvable problems from millions to tens of billions of unknowns, thereby addressing the crucial demand arising from practical applications in a sense. This paper provides a comprehensive review of state-of-the-art parallel approaches of the MLFMA, especially on a newly proposed ternary parallelization scheme and its acceleration on graphics processing unit (GPU) clusters. We discuss and numerically study the advantages of the ternary parallelization scheme and demonstrate its flexibility and efficiency.
MASSIVELY PARALLEL MULTILEVEL FAST MULTIPOLE ALGORITHM FOR EXTREMELY LARGE-SCALE ELECTROMAGNETIC SIMULATIONS: A REVIEW
2020-11-30
PIER
Vol. 169, 33-43, 2020
One-Way Topological States Along Vague Boundaries in Synthetic Frequency Dimensions Including Group Velocity Dispersion (Invited)
Qingrou Shan Danying Yu Guangzhen Li Luqi Yuan Xianfeng Chen
We recently proposed a two-dimensional synthetic space including one spatial axis and one synthetic frequency dimension in a one-dimensional ring resonator array [Opt. Lett. 41, 741 (2016)]. Nevertheless, the group velocity dispersion (GVD) of the waveguides that compose rings was ignored for simplicity. In this paper, we extend the previous work and study the topological one-way edge states in such a synthetic space involving GVD. We show that the GVD brings a natural vague boundary in the frequency dimension, so the topological edge state still propagates at several frequency modes unidirectionally along the spatial axis. Positions of such vague boundary can be controlled by changing the magnitude of the GVD. In particular, a relatively strong GVD can degrade this two-dimensional synthetic space to one-dimensional spatial lattice, but yet the one-way state is still preserved in simulations. Our work therefore exhibits the impact of the GVD on topological photonics in the synthetic space, which will be important for future practical experimental implementations.
ONE-WAY TOPOLOGICAL STATES ALONG VAGUE BOUNDARIES IN SYNTHETIC FREQUENCY DIMENSIONS INCLUDING GROUP VELOCITY DISPERSION (INVITED)
2021-12-24
PIER
Vol. 172, 33-40, 2021
Non-Hermitian Skin Effect and Delocalized Edge States in Photonic Crystals with Anomalous Parity-Time Symmetry
Qinghui Yan Hongsheng Chen Yihao Yang
Non-Hermitian skin effect denotes the exponential localization of a large number of eigen-states at boundaries in a non-Hermitian lattice under open boundary conditions. Such a non-Hermiticity-induced skin effect can offset the penetration depth of in-gap edge states, leading to counterintuitive delocalized edge modes, which have not been studied in a realistic photonic system such as photonic crystals. Here, we analytically reveal the non-Hermitian skin effect and the delocalized edge states in Maxwell's equations for non-Hermitian chiral photonic crystals with anomalous parity-time symmetry. Remarkably, we rigorously prove that the penetration depth of the edge states is inversely proportional to the frequency and the real part of the chirality. Our findings pave a way towards exploring novel non-Hermitian phenomena and applications in continuous Maxwell's equations.
NON-HERMITIAN SKIN EFFECT AND DELOCALIZED EDGE STATES IN PHOTONIC CRYSTALS WITH ANOMALOUS PARITY-TIME SYMMETRY
2022-04-30
PIER
Vol. 174, 33-42, 2022
TDFA-Band Silicon Optical Variable Attenuator
Maoliang Wei Hui Ma Chunlei Sun Chuyu Zhong Yuting Ye Peng Zhang Ruonan Liu Junying Li Lan Li Bo Tang Hongtao Lin
TDFA-band (2-μm waveband) has been considered as a promising optical window for the next generation of optical communication and computing. Absorption modulation, one of the fundamental reconfigurable manipulations, is essential for large-scale photonic integrated circuits. However, few efforts have been involved in exploring absorption modulation at TDFA-band. In this work, variable optical attenuators (VOAs) for TDFA-band wavelengths were designed and fabricated based on a silicon-on-insulator (SOI) platform. By embedding a short PIN junction length of 200 μm into the waveguide, the fabricated VOA exhibits a high modulation depth of 40.49 dB at 2.2 V and has a fast response time (10 ns) induced by the plasma dispersion effect. Combining the Fabry-Perot cavity effect and plasma dispersion effect of silicon, the attenuator could achieve a maximum attenuation of more than 50 dB. These results promote the 2-μm waveband silicon photonic integration and are expected to the future use of photonic attenuators in crosstalk suppression, optical modulation, and optical channel equalization.
TDFA-BAND SILICON OPTICAL VARIABLE ATTENUATOR
2020-10-02
PIER
Vol. 168, 31-38, 2020
A Novel Millimeter-Wave Backward to Forward Scanning Periodic Leaky-Wave Antenna Based on Two Different Radiator Types
Yiming Zhang Hui Liu Chenyang Meng Yuxin Lin Yuan Zhang Erik Forsberg Sailing He
A periodic millimeter wave leaky-wave antenna (LWA), which has two different types of radiator elements that enable backward to forward radiation, is proposed. The unit-cell of the LWA consists of two quarter-wavelength microstrip lines and two corrugated substrate integrated waveguide (CSIW) cells with S-shaped quarter-wavelength open-circuit stubs. In addition to two parallel edge radiators, a single etched transverse slot with a tilt angle acts as an ancillary radiator, which ensures impedance matching in a large frequency range and achieves the backward to forward scanning. We analyze the proposed design through simulations, characterize a fabricated prototype and find it to have good radiation properties including broad impedance bandwidth. The measurement results show a high peak gain from 11 to 15.8 dBi with a large scanning angle range from -34° to +22° in the K-band operating frequency range.
A NOVEL MILLIMETER-WAVE BACKWARD TO FORWARD SCANNING PERIODIC LEAKY-WAVE ANTENNA BASED ON TWO DIFFERENT RADIATOR TYPES
2022-07-27
PIER
Vol. 175, 29-43, 2022
Low Cost and High Performance 5-Bit Programmable Phased Array Antenna at Ku-Band
Xin Li Han Qing Yang Rui Wen Shao Feng Zhai Guo Biao Liu Zheng Xing Wang Hong Fei Gao Ge Fan Jun Wei Wu Qiang Cheng Tie-Jun Cui
We present a low-cost and high-performance 5-bit programmable phased array antenna at Ku-band, which consists of 1-bit reconfigurable radiation structures, digital phase shifters, and coplanar waveguide feeding network. The 1-bit reconfigurable radiation structure utilizes symmetric geometries and PIN diodes to form stable 180° phase difference. The digital phase shifter provides 168.75° phase difference and together with the radiation structure form a 348.75° phase coverage. The antenna operates between 14.4 and 15.4 GHz, and the overall array contains 24×2 elements with each of them being individually addressable. By changing the states of the diodes and thus adjusting the phase coding sequences of the array, the antenna achieves 0°-60° precise beam scanning at 14.8 GHz, with the sidelobe level, cross-polarization, and gain fluctuation being less than -16 dB, -26 dB, and 2.4 dB, respectively. A prototype was fabricated to verify the design, and the measurement results agree well with simulations. Compared with traditional phased arrays composed of numerous phase shifters and T/R components, the proposed antenna features high performance, high flexibility, low profile, and low cost. The antenna provides a new and feasible solution of wavefront steering and will benefit the various application scenarios.
LOW COST AND HIGH PERFORMANCE 5-BIT PROGRAMMABLE PHASED ARRAY ANTENNA AT KU-BAND
2020-11-25
PIER
Vol. 169, 25-32, 2020
Designer Surface Plasmons Enable Terahertz Cherenkov Radiation (Invited)
Jie Zhang Xiaofeng Hu Hongsheng Chen Fei Gao
Cherenkov radiation (CR) is a promising method to generate high-power terahertz (THz) electromagnetic (EM) waves, which are highly desired in numerous practical applications. For the purpose of economy energy, naturally occurred materials with flat surface (e.g. graphene), which can support highly-confined surface-plasmon-polariton (SPP) modes, have been proposed to construct high-efficiency terahertz CR source; however, these emerging materials cannot be easily fabricated nor flexibly designed. Here, we propose a designer-SPP metamaterial scheme to pursue terahertz CR. The metamaterial is a structure-decorated metal surface, which is compatible with planar fabrication, and can support SPP-like EM modes in terahertz frequencies, also named as designer SPP. Due to the structure dependence of designer SPP, its dispersions can be flexibly designed by changing the structure geometries as well as choosing proper dielectric medias. Numerical results clearly demonstrated this scheme. Our proposal may promise future high-efficiency and intense THz source with design flexibilities.
DESIGNER SURFACE PLASMONS ENABLE TERAHERTZ CHERENKOV RADIATION (INVITED)
2020-08-30
PIER
Vol. 168, 25-30, 2020
Second-Order Nonlinear Susceptibility Enhancement in Gallium Nitride Nanowires (Invited)
Kangwei Wang Haoliang Qian Zhaowei Liu Paul K. L. Yu
We report the second-harmonic generation (SHG) from single GaN nanowire. The diameter of the GaN nanowire varies from 150 to 400 nm. We present a model for the SHG process in the GaN nanowire; the analysis shows quantitatively that the SHG is dominated by its surface area. The effective second order nonlinear optical susceptibility (χ(2)eff) increases as the diameter of the GaN nanowire decreases. For 150-nm diameter GaN nanowire, χ(2)eff reaches 136 pm/V.
SECOND-ORDER NONLINEAR SUSCEPTIBILITY ENHANCEMENT IN GALLIUM NITRIDE NANOWIRES (INVITED)
2022-03-04
PIER
Vol. 173, 25-36, 2022
Portable 4D Snapshot Hyperspectral Imager for Fastspectral and Surface Morphology Measurements (Invited Paper)
Jing Luo Zijian Lin Yuxin Xing Erik Forsberg Chengdong Wu Xinhua Zhu Tingbiao Guo Gaoxuan Wang Beilei Bian Dun Wu Sailing He
A portable 4D snapshot hyperspectral imager (P4DS imager) with compact size, fast imaging time, low cost, and simple design is proposed and demonstrated. The key components of the system are a projector, a liquid crystal tunable filter (LCTF), and a camera. It has two operating modes dependent on the set state of the LCTF: a 3D light measurement mode that produces a 3D point cloud reconstruction of the object, and a hyperspectral imaging mode yielding spectral data. The camera imaging plane is the same for both operating modes allowing the collected spatial and spectral data to be directly fused into a 4D data set without post-processing. The P4DS imager has excellent performance with a spectral resolution of 10 nm, a spatial depth accuracy of 55.7 um, and total 4D imaging time of 0.8 s. 4D imaging experiments of three different samples, colored doll statue, green broccoli, and a human face, are presented to demonstrate the efficiency and applicability of the system. Due to being cost-effective, portable, and good imaging performance, the proposed system is suitable for commercialization and mass production.
PORTABLE 4D SNAPSHOT HYPERSPECTRAL IMAGER FOR FASTSPECTRAL AND SURFACE MORPHOLOGY MEASUREMENTS (INVITED PAPER)
2022-04-29
PIER
Vol. 174, 23-32, 2022
Squeezing of Hyperbolic Polaritonic Rays in Cylindrical Lamellar Structures
Lu Song Lian Shen Huaping Wang
We propose the squeezing of hyperbolic polaritonic rays in cylindrical lamellar structures with hyperbolic dispersion. This efficient design is presented through conformal mapping transformation by combining with circular effective-medium theory (CEMT) that is adopted to predict the optical response of concentric cylindrical binary metal-dielectric layers. The volume-confined hyperbolic polaritons supported in these cylindrical lamellar structures could be strongly squeezed when they propagate toward the origin since their wavelength shortens, and velocity decreases. To demonstrate the importance of using CEMT for engineering highly-squeezed hyperbolic polaritons, both CEMT and planar effective-medium theory (PEMT) are utilized to design the cylindrical lamellar structures. It is shown that the PEMT-based design is unable to achieve hyperbolic polaritons squeezing even with a sufficiently large number of metal-dielectric binary layers. Remarkably, this study opens new opportunities for hyperbolic polaritons squeezing, and the findings are promising for propelling nanophotonics technologies and research endeavours.
SQUEEZING OF HYPERBOLIC POLARITONIC RAYS IN CYLINDRICAL LAMELLAR STRUCTURES