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We explore the mode conversion characteristics of electrostatic hybrid surface waves due to the magnetic field orientation in a magnetoplasma slab. We obtain the dispersion relations for the symmetric and anti-symmetric modes of hybrid surface waves for two different magnetic field configurations: parallel and perpendicular. For the parallel magnetic field configuration, we have found that the symmetric mode propagates as upper- and lower-hybrid waves. However, the hybrid characteristics disappear and two non-hybrid waves are produced for the anti-symmetric mode. For the perpendicular magnetic field configuration, however, the anti-symmetric mode propagates as the upper- and lower-hybrid waves and the symmetric mode produces two non-hybrid branches of waves. [ABSTRACT FROM AUTHOR]

We propose an all-optical approach for simultaneous high bit-rate return-to-zero (RZ) to non-return-to-zero (NRZ) format and LP 01 to LP 11 mode conversion using a weakly tilted apodized few-mode fiber Bragg grating (TA-FM-FBG) with specific linear spectral response. The grating apodization profile is designed by utilizing an efficient inverse scattering algorithm and the maximum refractive index modulation is adjusted based on the grating tilt angle, according to Coupled-Mode Theory. The temporal performance and operation bandwidth of the converter are discussed. The approach provides potential favorable device for the connection of various communication systems. [ABSTRACT FROM AUTHOR]

In this work, a novel baseline-free procedure aimed at detecting and sizing delaminations in composite plates is proposed. To such a purpose an air-coupled probe is used to measure the sound pressure in air that is generated by leaky guided waves traveling along the plate and scattered by defects. In particular, by scanning the plate surface with a proper probe tilt angle and lift-off, wavefields dominated by a single guided mode can be obtained. Then, a processing procedure based on warped time–frequency operators is used to filter out the main wavefield generated by the acoustic source in order to enhance the one scattered by defects. Such operators are designed basing on the dispersion curves of the dominant guided mode considered. Finally, it is shown how the scattered wavefield can be further processed to infer the defect position and size by means of the Circular Hough Transform. The presence of a barely visible delamination on a 4.9 mm thick composite laminate was detected by exploiting the proposed approach. The obtained results are in good agreement with those obtained by using a commercial phased-array ultrasonic C-scan device. [ABSTRACT FROM AUTHOR]

To make clear the mode conversion behavior of S0-mode lamb wave and SH0-plate wave converting to the longitudinal mode guided wave and torsional mode guided wave in a pipe, respectively, the experiments were performed based on a previous built pipe inspection system. The pipe was wound with an L-shaped plate or a T-shaped plate as the waveguide, and the S0-wave and SH0-wave were excited separately in the waveguide. To carry out the objective, a meander-line coil electromagnetic acoustic transducer (EMAT) for S0-wave and a periodic permanent magnet (PPM) EMAT for SH0-wave were developed and optimized. Then, several comparison experiments were conducted to compare the efficiency of mode conversion. Experimental results showed that the T(0,1) mode, L(0,1) mode, and L(0,2) mode guided waves can be successfully detected when converted from the S0-wave or SH0-wave with different shaped waveguides. It can also be inferred that the S0-wave has a better ability to convert to the T(0,1) mode, while the SH0-wave is easier to convert to the L(0,1) mode and L(0,2) mode, and the L-shaped waveguide has a better efficiency than T-shaped waveguide. [ABSTRACT FROM AUTHOR]

Electron temperature and plasma density was measured with change of working air pressure by Langmuir probe at a given power. Radio-frequency (rf) inductively coupled plasma (ICP) discharge mode conversion is determined by optical emission spectrum (OES) with the increase of gas pressure at different power. The results indicate that plasma discharge mode can change from E mode to H mode and spectral intensity appears inverse hysteresis phenomenon with the change of air pressure. The hysteresis width decreases with the increase of power and the hysteresis is no longer present when the power is 420 W and 435 W. Moreover, the jump pressure of E-H transition is gradually reduced with the corresponding increase of discharge power. ICP discharge mode appears E-H-E phenomenon with the increase of air pressure. [ABSTRACT FROM AUTHOR]

A performance enhanced butt coupling structure incorporating a vertically and laterally tapered SiON polymer core on silicon (Si) to tunnel and widen propagating optical modes of adiabatic taper is proposed. The proposed structure can effectively overcome the strong back reflections caused at the interface between fiber and Si nanowire to enable higher coupling efficiency. The placement of the SiON polymer core is chosen to restrict the passage of light through the bottom cladding to avoid unnecessary leakage. The performance of the structure is characterized for distinct features, including taping length, coupling efficiency, and coupling bandwidth for both single as well as cacaded configurations, compared with the state-of-the-art grating coupler. It is found that, with the right set of design specifications, butt couplers can outperform grating couplers in both coupling efficiency and bandwidth, although grating couplers are considered friendlier for wafer-level testing. [ABSTRACT FROM PUBLISHER]

This paper presents the design of a 5-channel driver array IC with a high total output current of 5\times \text 120 mA and a 6~\mathrm V\mathrm {pp} differential output voltage in SiGe bipolar technology. Special attention is given to design considerations for stable electrical and thermal operation and to the minimization of cross-coupling between the array channels. The related driver array is intended to realize a low-cost, small footprint 10\times \text 11.3 Gbit/s dense wavelength division multiplexing transmitter assembly, consisting of a pair of two driver ICs with a chip-to-chip bondwire interface to a ten-channel Mach–Zehnder modulator (MZM) in a photonic integrated circuit (PIC). The driver IC contains all required components, including the far-end terminations of the MZMs as well as an energy-efficient concept for flexible MZM biasing. Current hogging in the transistors of the output stages is mitigated by a novel circuit concept that is introduced along with an electro-thermal model for dense multi-transistor arrangements, especially in driver output stages. The performance of the design is demonstrated by measurement results of the driver array IC in both standalone and integrated PIC assemblies. [ABSTRACT FROM AUTHOR]

In this paper, the LP11 mode evolution in a few mode-polarization maintaining fiber is experimentally investigated. Selective conversion from the LP11a/LP11b mode to the LP11b/LP11a , OAM+1, and OAM−1 modes are demonstrated with varying wavelengths and fiber lengths. This property may have nice applications in spatial division multiplexing (SDM) systems, and one of them, i.e., the all-fiber compact and robust scalar orbital angular momentum (OAM) generator, which is cascaded by a mode-selective coupler and a few mode-polarization maintaining fiber, is also demonstrated with expected performance for conversion between LP01 mode and OAM+1/OAM−1. [ABSTRACT FROM PUBLISHER]

Propagation of Hypergeometric-Gaussian laser beam in a nonlinear plasma medium is investigated by considering the Source Dependent Expansion method. A subfamily of Hypergeometric-Gaussian beams with a non-negative, even and integer radial index, can be expressed as the linear superposition of finite number of Laguerre–Gaussian functions. Propagation of Hypergeometric-Gaussian beams in a nonlinear plasma medium depends on the value of radial index. The bright rings’ number of these beams is changed during the propagation in plasma medium. The effect of beam vortex charge number l and initial (input) beam intensity on the self-focusing of Hypergeometric-Gaussian beams is explored. Also, by choosing the suitable initial conditions, Hypergeometric-Gaussian subfamily beams can be converted to one or more mode components that a typical of mode conversion may be occurred. The self-focusing of these winding beams can be used to control the focusing force and improve the electron bunch quality in laser plasma accelerators. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study on the interaction of ultrasonic guided waves with delamination in the web–flange interface of a co-cured, co-bonded composite T-joint. A complex interaction of waves is induced, first, by one, and, later, by two piezoceramic wafer(s) bonded on the inner surface of the flange. The flange surface velocity distributions are reconstructed from the scanning laser Doppler velocimeter (LDV) measurements to study the effect of a delamination overlapping the web–flange interface. The surface-bonded piezoelectric actuator(s) placed remotely on the flange produce primarily anti-symmetric wave incidence to the delamination. A two-stage wave mode conversion process, one due to the web and joint filler, and the other due to the delamination underneath the flange is observed. First, we address the problem of identification of delamination by ultrasonic contrast imaging of the web–flange interface using a single actuator. This study is extended further to enhance the ultrasonic contrast imaging at the web–flange interface using a standing wave. A quantitative methodology based on mode conversion strength is developed to monitor different structural features like free-edge, web–flange interface and delamination. The results show the complex nature of the conversion of flexural waves to in-plane waves through the deltoid and along the web–flange interface. [ABSTRACT FROM AUTHOR]

This paper reports on a spurious mode suppression technique for S0 mode aluminum nitride (AlN) laterally vibrating resonators. The technique utilizes a notch in the resonator body to convert spurious asymmetrical (A0) modes into the intended S0 mode vibration. Finite-element analyses were employed to theoretically investigate the mode conversion from A0 mode to S0 mode, and identify the optimal notch configuration. The technique has been experimentally validated to simultaneously eradicate the A0 spurious mode and enhance the S0 mode electromechanical coupling ( kt^{2} ) for the monolithically integrated resonators over a wide frequency range ( $100\sim 600$ MHz). It is a crucial technology development, because the spurious modes are a major bottleneck obstructing the deployment of single-chip multi-frequency AlN resonators as a commercially viable solution for radio frequency front-end filtering. [2015-0295] [ABSTRACT FROM PUBLISHER]

In this paper, the concepts of weak coupling and weak imbalance are exploited to investigate crosstalk and mode conversion occurring in perfectly balanced differential lines (DLs) due to proximity with other DLs printed on the same PCB substrate. Approximate modal circuits are derived, where the aforementioned phenomena are accounted for by the use of distributed voltage and current sources. This allows evidencing the relevant parameters at the basis of these undesired phenomena, which may significantly degrade DL performance in terms of emission and immunity properties as well as signal integrity. Accuracy of the proposed model, preliminary validated versus exact solution of transmission line equations, is eventually assessed through vector network analyzer measurements carried out on a PCB sample. [ABSTRACT FROM AUTHOR]

Deep-subwavelength guiding and superfocusing of spoof surface plasmon polaritons (SSPPs) realized on a helically grooved metal wire at microwave frequencies are presented in this paper. Two smooth bridges with gradient helical grooves decorated on the cylindrical and conical metal wire are proposed and designed, respectively. High-efficiency and broadband mode conversion from the traditional guided waves to the SSPPs and superfocusing of SSPPs are reported. Numerical simulations quantitatively show that the amplitudes of electric field at the tip of the conical wire with gradient helical grooves can be magnified 50 times more than that of the input signal in broadband. Moreover, the second transition structure ensures that the depth of helical groove can be tuned flexibly and arbitrarily, making it compatible with all kinds of N-type coaxial connectors. Strong field concentration and superfocusing of these two structures can be easily extended to terahertz (THz) frequencies by tuning the geometrical parameters and can find important applications in sensing, spectroscopy and near-field imaging in the microwave and THz frequencies. [ABSTRACT FROM AUTHOR]