查看更多>>摘要：A tunable terahertz (THz) dual-band circularly polarized (CP) dielectric resonator (DR) antenna (DRA) is numerically analysed and implemented. Initially, an aperture coupled dual-band rectangular DRA is designed. This operates with the fundamental mode in the lower band and third order mode in the upper band and provides the linearly polarized response. The diagonal corners of the rectangular DR are truncated for obtaining the orthogonal degenerate components of the operating modes and thus the CP response is achieved. The tunability is achieved in the frequency response by applying a monolayer graphene material coating at the radiating surface of the chamfered DR. The antenna offers 10 dB impedance bandwidth of 18.41% (3.21 -3.86 THz) and 4.7% (4.77 -5.0 THz) along with 3 dB axial ratio bandwidth of 3.48% (3.38 -3.5 THz) and 1.39% (4.98 -5.05 THz). Furthermore, the proposed tunable dual-band THz CPDRA provides the gain of more than 6 dBic along with the radiation efficiency of more than 95% in each operating band.
查看更多>>摘要：In quantum computers, all the heavy computations are done through quantum processors. ALU is one of the most significant parts of every processor responsible for performing logical operations and primary binary operations. All of the arithmetic computations in ALU utilize adder/subtractor to produce the expected result. Fault-tolerant circuit designs have found increasing application in quantum computers regarding the noise sensitivity of qubits and the faulty environment in which they operate. Additionally, reversible quantum circuits can prevent heat circulation and information lost throughout the high-rate binary calculations. The primary subject is the development of digital reversible fault-tolerant quantum circuits with higher performance and more efficiency regarding the number of inputs and outputs employed by quantum gates, depth, and delay. Full adders and subtractors are highly significant in different parts of quantum digital circuits and are used widely in multipliers, dividers, ALUs, and floating-point operations. In this paper, applying the parity-preserving method and the properties of Boolean algebra two novel reversible fault-tolerant designs are proposed that can detect every single or the odd number of errors. Also, both proposed designs are capable to perform addition and subtraction operations by changing the control signal(ctr). Our offered designs can reduce energy loss in the form of emitted heat in circuits, reduce the cost of building quantum circuits, reduce computation time, and detect errors in case of happen. Furthermore, comprehensive simulations for each possible combination of inputs and corresponding outputs are done to prove the full functionality and accurate performance of the proposed designs.
查看更多>>摘要：The surface property of rough target can cause the decoherence and depolarization effects, which is among the main limiting factors in heterodyne detection. In the decoherence analyses, the phase fluctuation model of laser echo from rough target is established based on the spectral density method, and the phase fluctuations under typical roughness conditions are obtained by Monte Carlo method. The distribution properties of heterodyne signal amplitudes are analyzed under different surface height fluctuation and correlation length T. Then the corresponding experiments are carried out, which show that the phase fluctuations of laser echo satisfy the Gaussian distribution, and the decoherence effect induces the reductions and fluctuations of heterodyne signal amplitudes, especially with larger roughness surface. For typical rough metal targets, the depolarization characteristics of laser echoes from different scattering positions are obtained, which suggest that the depolarization effect increases with the rise of roughness. The positive correlation between the decoherence and depolarization effects provides a reference for the design of heterodyne lidar system, and the statistics can also be adopted for target roughness inference and target type identification.
查看更多>>摘要：Multi-frequency fringe projection profilometers that rely on temporal phase unwrapping require frequency selection that provides minor unwrapping errors with the smaller number of fringe patterns projected. The frequency selection presents a scale-insensitive property for 3D profilometers that is analysed and investigated by analytical, simulation and practical means in this work. This property has been tested in an experimental profilometer with a parallel axis optical configuration. The scale-insensitive performance of the temporal phase unwrapping is analysed over a range of Field of Views (FOVs). It is shown that after typical calibration procedures, the scaling constants of the temporal phase unwrapping remain constant for different scales of FOVs. Additionally, a theoretical relation among fringes period in emitters of Digital Light Processors (DLPs) and camera detectors for the fringe profilometer used is presented and confirmed by experimental results.
Lopera, Jhon A.Cardenas, Ana M.Granada Torres, Jhon J.Zapata, Juan D....
10页
查看更多>>摘要：In this paper, we propose and numerically analyze a colorless transmitter based on a Fabry- Perot Laser Diode (FPLD) with an emission wavelength that is externally tuned using a spectral sliced super luminescent diode. The Fabry-Perot based colorless transmitter is designed to support 100 GHz spaced longitudinal modes with a central wavelength of 1552.525 nm. We study the cavity's end-facets reflectivity, in order to determine a configuration that allows a low injection power requirement with high transmission performance. Finally, we analyze the transmission performance of the colorless transmitter in a Passive Optical Network (PON) at 2.5 Gbps bit rate with a Non-Return-to-Zero (NRZ) using the following configuration: transmission distances up to 120 km, seeding carrier with 3-dB bandwidths (12.5 GHz, 25 GHz and 50 GHz), two optical channels at 1552.525 nm (central mode) and 1550.125 nm (fourth side mode). The results show that reflectivities of 10% and 90% for the front-facet and the end-facet, respectively, allow a good trade-off between the injection power requirement for tuning the colorless source avoiding the inter-channel interference, and the transmission performance in terms of Bit Error Rate (BER). Thus, in all scenarios, it is possible to obtain Side Mode Suppression Ratios (SMSR) above 30 dB using injection power below to 0.3 mW. Besides, an error-free transmission is achieved for distances over 25 km, in the case with the injection carrier is less than 25 GHz 3-dB bandwidth. Hence, the proposed colorless source can be a suitable feasible solution to implement optical access networks.
Arfan, M.Ghaffar, A.Alkanhal, Majeed A. S.Naz, M. Y....
8页
查看更多>>摘要：We studied the orbital angular momentum (OAM) wave scattering by a perfect electromagnetic conductor (PEMC) sphere using Mie Theory. The Vortex Electromagnetic (VEM) wave is well known with a definite amount of OAM. To obtain the OAM wave scattering from PEMC sphere, the conventional plane wave scattering from PEMC sphere expressions are modified by taking into account the characteristics of OAM waves. The unique properties of analytical expression of OAM fields are analyzed, and the scattered field coefficients in terms of incident field coefficients were obtained using boundary conditions. The comparison between conventional scattering for plane wave and OAM wave from PEMC sphere had been carried out. The presented work provides a theoretical insight for the calculation of Radar Cross Section (RCS) by metamaterial as PEMC sphere and identification applications of light carrying OAM in optical manipulation technology.
Ghafoor, ImranTse, Peter W.Munir, NaumanTrappey, Amy J. C....
15页
查看更多>>摘要：Railhead defects must be detected and classified intelligently in order for railway transportation systems to operate safely. Rail defect identification and categorization can be automated by using machine learning models to process rail image data (acquired using cameras). However, such an automated method has significant drawbacks: it cannot detect subsurface defects, picture data requires a high-end GPU with a long computational time, and machine learning model training can be influenced by image quality, which is dependent on light intensity and shooting altitude. Rayleigh waves are a potential candidate for rail inspection because they can detect both surface and subsurface defects and travel long distances on curved surfaces (like a rail) at high speed. This article looks into the possibility of combining fully non-contact laser ultrasonic technology (LUT) and a deep learning approach for intelligent detection and classification of railhead surface and subsurface defects. The fully non-contact LUT was used to actuate and capture laser-generated Rayleigh wave signals on railhead specimens in order to create a database of A-scan signals from healthy, surface, subsurface, and edge defect railheads. The classification capabilities of a support vector machine (SVM), a fully connected deep neural network (DNN), and a convolutional neural network (CNN) were examined after they were applied to the preprocessed signals without extracting any statistical/signal processing-based characteristics. The comparative analysis demonstrates that CNN is robust in classifying railhead defects. As a result, when combined with CNN, the laser ultrasonic technology may ensure automatic defection and classification of railhead surface and subsurface flaws.
查看更多>>摘要：In this article, the extended F-expansion method is applied to secure cubic-quartic optical solitons for twin-core couplers with polynomial law of nonlinearity. Bright, singular, and bright- singular combo cubic-quartic solitons are derived. Also, periodic solutions, combo periodic solutions, exponential solutions and rational solutions are obtained. Moreover, for the physical illustration, some of the obtained solutions are represented graphically.
查看更多>>摘要：We study the propagation of ultrashort-pulses in asymmetric twin-core optical waveguide represented by the variable-coefficient higher-order nonlinear Schrodinger equation with complex potential and source term. We investigate the presence of localized as well as periodic solutions using self-similarity transformation and fractional transformation technique. Dynamical evolution of these solutions is studied through the judicious choice of tapering profile and source parameter. Our exact analysis helps us to identify the inhomogeneous waveguide to satisfy the PT-symmetric property.
查看更多>>摘要：We report on a novel fiber chirped-pulse amplification system with a hundred-watt level average power. All-fiberized laser amplifiers, a chirped fiber Bragg grating stretcher, and a chirped volume Bragg grating compressor make up the system. The chirped fiber Bragg gratings were inscribed in the experiment through the fabrication system built by ourselves, with the parameters fine-tuned during fabrication to match the spectrum after stretching to the source waveband and the spectral width of the chirped volume Bragg grating compressor. A 12 m-long photonic crystal fiber was also used to provide effective spectral bandwidth matching between the preamplifier and the chirped fiber Bragg gratings. Meanwhile, the gain fiber length of the amplifiers was suitably selected, and the overall system's spectral matching was achieved. As a result, a compressed average power of 111.4 W was obtained with a pulse duration of 1.5 ps, resulting in peak power of 4.1 MW. The proposed all-fiberized stretcher and amplifier structure significantly decrease the system's volume, increase the system's stability and dependability, and may be used in various applications.
NSTL
Elsevier