Complex Electric Field Research Articles

Performance of a multianode straw tube detector

We report on the performance of a multianode straw tube detector using cosmic rays. It is constructed inside a 5cm diameter straw tube with twelve anode wires. A calibration technique and track reconstruction algorithm is developed for this type of detector, and we calculate the resolution from the residual distribution and show that ~170μm resolution is not difficult to achieve. The technique is general and especially useful for detectors with complex electric fields with or without the magnetic field.

The electrostatic plasma environment of a small airless body under non-aligned plasma flow and UV conditions

Airless bodies interact with a wide variety of plasma environments throughout the solar system. For many objects, incident plasma is nearly co-aligned with solar ultraviolet radiation leading to the development of a positively charged dayside photoelectron sheath and a negatively charged nightside plasma sheath. Other objects, however, are present in environments where the plasma flow and solar UV radiation may not co-align. These environments include, for example, the moons of Mars as they pass through the deflected Martian magnetosheath, and many of the moons of the outer planets, which are embedded in co-rotating planetary magnetospheres. The decoupling of the plasma flow and UV incidence vectors opens up a wide range of possible surface charging and near-object plasma conditions as a function of the relative plasma-UV incidence angle. Here, we report on a series of simulations of the plasma interaction of a small body (effectively smaller than both electron and ion gyroradii) with both flowing plasma and UV radiation for different plasma-UV incidence angles using an electrostatic treecode model. We describe the plasma and electric field environment both on the object surface and in the interaction region surrounding the object, including complex surface charge and electric field distributions, interactions between surface-generated photoelectrons and ambient plasma electrons, and complex potential distributions, all of which vary as a function of the relative plasma flow-UV angle. We also show that in certain conditions, non-monotonic potential structures may exist around such objects, partially similar to those found at Earth's Moon.

Single shot, time-resolved measurement of the coherence properties of OCT swept source lasers.

A novel, time-resolved interferometric technique is presented that allows the reconstruction of the complex electric field output of a swept source laser in a single-shot measurement. The power of the technique is demonstrated by examining a short cavity swept source designed for optical coherence tomography (OCT) applications with a spectral width of over 100 nm. The novel analysis allows a time-resolved real-time characterization of the roll-off, optical spectrum, linewidth, and coherence properties of a dynamic, rapidly swept laser source.

Nonlinear pulse propagation in InAs/InP quantum dot optical amplifiers: Rabi oscillations in the presence of nonresonant nonlinearities

We study the interplay between coherent light-matter interactions and non-resonant pulse propagation effects when ultra-short pulses propagate in room-temperature quantum-dot (QD) semiconductor optical amplifiers (SOAs). The signatures observed on a pulse envelope after propagating in a transparent SOA, when coherent Rabi-oscillations are absent, highlight the contribution of two-photon absorption (TPA), and its accompanying Kerr-like effect, as well as of linear dispersion, to the modification of the pulse complex electric field profile. These effects are incorporated into our previously developed finite-difference time-domain comprehensive model that describes the interaction between the pulses and the QD SOA. The present, generalized, model is used to investigate the combined effect of coherent and non-resonant phenomena in the gain and absorption regimes of the QD SOA. It confirms that in the QD SOA we examined, linear dispersion in the presence of the Kerr-like effect causes pulse compression, which counteracts the pulse peak suppression due to TPA, and also modifies the patterns which the coherent Rabi-oscillations imprint on the pulse envelope under both gain and absorption conditions. The inclusion of these effects leads to a better fit with experiments and to a better understanding of the interplay among the various mechanisms so as to be able to better analyze more complex future experiments of coherent light-matter interaction induced by short pulses propagating along an SOA.

1211 Development of Novel Computer Generated Hologram (CGH) for Short Pulse Laser Processing of Precise Micro Pattern Using Spatial Light Modulator

Complex micro- and nano-structure can be formed simply by generating complex electric fields holographically with a spatial light modulator (SLM) by liquid crystal on silicon (LCOS) technology. Processing patterns for micro-patterns to be desired are commonly generated by computer generated hologram (CGH). In this study, to realize the more precise micro-processing with highly flexible pattern by use of the LCOS-SLM, a novel CGH algorithm suitable to micrometer order processing is developed, into which the principle of a phase shift mask is applied. From the results of processing experiments to form micro holes and longitudinal ridges, the novel algorithm can provide more precise processing.

Исследование анизотропии проводимости внутренних параметров электродов электролизеров химической промышленности

Modeling of the internal contact connections resistance of electrolysis plants is important to a problem solution of energy savings in companies with energy-intensive production with rated currents of 40-150 kA that is a complex mathematical problem. In electrolytic plants, suppression grids, steeped into the solution in the electrolytic bath, are used as electrodes, and their deformation leads to an uneven current distribution on the electrode surface and insufficient performance of the electrolyser. It is suggested to produce electrodes of perforated steel sheets. Using calculation of complex electric fields, a method for optimizing the geometrical characteristics of the electrolysis baths has been developed, in order to reduce their internal resistance and even current distribution in them. The value of the electrolyser’s conductivity has been obtained, depending on apertures radius, the distance between their centers and sheets’ thickness. The electrodes modeling and a study of their conductivity have been performed; conductivity values of the electrolysis bath have been obtained, depending on the changes in these parameters.

An Electrochromic Phosphorescent Iridium(III) Complex for Information Recording, Encryption, and Decryption

Electrical stimuli‐induced change in absorption spectra, or electrochromism, has been well studied due to its promising applications in displays, sensors, smart windows, memory chips, and electronic papers, etc. However, electrochromic luminescent materials are rather scarce. In view of their advantages including easy tuning of luminescence color, short response time, and relatively high contrast, an electrochromic phosphorescent Ir(III) complex (IrOH) with an OH moiety in the N^N ligand is designed. This complex displays long‐lived phosphorescence, whose wavelength and lifetime are very sensitive to complex concentration, pH value, and electric field. Based on the interesting electrochromic phosphorescence of complex IrOH, a quasi‐solid information recording and storage device has been designed. A short‐lived fluorescent dye has been selected to encrypt the recorded information. In view of the much longer lifetime of IrOH compared with that of the fluorescent dye, decryption has been accomplished by using time‐resolved imaging techniques. Hence, it is believed that electrochromic phosphorescence will open up a new and efficient avenue for applications in information encryption and decryption.

Experimental and theoretical investigation on the thermo-electro-elastic properties of Macro-Fiber Composites (MFC)

The effective thermo-electro-elastic properties of Macro-Fiber Composites (MFC) are evaluated by means of an analytical model based on ‘equivalent layered approach’ using the concepts of ‘rule of mixtures’ and ‘series and parallel capacitance theory’. To account for the complex electric field distribution and the constituents shape and position, a numerical model based on finite element calculations is developed using ‘unit-cell approach’. The piezoelectric charge constants of MFCs are experimentally evaluated by applying electrical load in various thermal environment (27°C to 70°C). The proposed models are validated with the results available in literature, experimental values and the data from the manufacturer. Also, effect of thermal environment on the effective constants of MFCs for various volume fraction of piezoceramic phase is investigated.

Nitrogen Effect on the Frequency Shift in Indium-GaAsN Quantum Wells Laser

The GaAsN/GaAs material system has recently been investigated as material for the realization of high-performance laser diodes emitting at the optical fiber window. Nitrogen content in GaAsN has a great influence on the band gap in this semiconductor. The knowledge of influence of nitrogen on optical transition energies in GaAsN/GaAs Quantum Wells (QWs) or Quantum Dots (QDs) structures is very important due to the possibility of adjustment of the optical transition energies to the telecommunication wavelength range when the system GaAsN is submitted to further indium elements giving rise to the quaternary alloys (In)GaAsN. The purpose of this work is to solve the coupled nonlinear rate equations describing the complex electric field and the carrier density in a simple model of the GaNxAs1-x or (In)GaAsN semiconductor laser. The model is sufficient to account for many of the observed dynamics in a single mode semiconductor laser in response to a dynamic drive current, such as relaxation oscillations and frequency chirping.

Electroporation as a New Cancer Treatment Technique: A Review on the Mechanisms of Action

Electroporation is a highly effective method to increase permeability of cell membrane by using series of short intense electric pulses. Using this technique, we can introduce small and large molecules into cells. The electroporation of biological membranes has various applications in molecular biology and medicine. Despite the numerous applications of electroporation, the detailed effects of electric pulse on biological membranes as well as exact mechanisms of pore formation in living cells are not well understood. Several in-vitro and in-vivo experimental studies have been conducted to determine the mechanisms of action of electroporation in various types of membranes. Because of the small spatial and fast temporal scales of this process, direct observation of electroporation is difficult, theoretical models and molecular dynamic simulations have been developed to facilitate the interpretation of experimental data and the understanding of the mechanisms of action of electroporation. The role of phospholipids in respond to external electric fields, behavior of water dipoles in the complex electric field landscape of the membrane interface and reorganization of water dipoles in pore formation process have been proposed in these studies. Pore characteristics such as life time, ion selectivity, size, kinetics of formation as well as number of pores are significant factors in the proposed mechanism of action. The present study reviews the different mechanisms of action of electroporation proposed by different experimental and modeling studies.

Tuning of 2.998 GHz S-band hybrid buncher for injector upgrade of LINAC II at DESY

The injector upgrade of LINAC II at DESY aims to improve its reliability and mitigate the radiological activation of components due to electron loss at relatively high energy of hundreds of MeV. Therefore, a 2.998GHz hybrid buncher has been developed and will be installed in between an existing 2.998GHz pre-buncher and LINAC II. It comprises a 1-cell standing-wave (SW) section for rapid electron acceleration and a 13-cells traveling-wave (TW) section for further beam bunching and acceleration. This paper focuses on its radio-frequency tuning procedure. The tuning strategy combines a non-resonant bead-pull measurement of complex electric field and a linear model for local reflection coefficient calculation. It is demonstrated that imaginary part of the local reflection coefficient represents the field distribution straightforwardly, based on which the structure can be tuned from cell to cell. During tuning, special attention has been paid to the field enhancement in the SW section to ensure its beam-capturing capability. Field amplitude and phase, global and local reflection coefficients have been analyzed for two different frequencies simultaneously, i.e. the intrinsic frequency of the structure and the target frequency, to avoid over-tuning. The tuning result is satisfying. For the target frequency, field unflatness of the TW section has been reduced from ±9% to ±4%, and field in the SW section has been enhanced significantly. Meanwhile, in the TW section, the deviation of phase advances between adjacent cells from the nominal value 120° has been reduced from the range ±5° to ±2°. By using ASTRA simulation, it has been verified that the residual detuning of the structure is acceptable in view of the beam dynamics performance.

Two-dimensional relativistic particle-in-cell code for simulation of laser-driven ion acceleration in various acceleration schemes

Results of a new relativistic two-dimensional particle-in-cell code for simulation of laser-driven ion acceleration are presented. It is shown that a complex electric field structure arose during the laser–target interaction as well as the evolution of the ion and electron concentration for the laser-induced cavity pressure acceleration scheme took place. During computation the influence of parameters such as target thickness and width, target starting position inside cavity and its atomic composition, as well as laser pulse length and beam width are examined. Values adopted for the calculation reflect the experimental conditions.

Multidimensional QKD Based on Combined Orbital and Spin Angular Momenta of Photon

It has been widely recognized that the underlying principles of quantum mechanics could be used to enable secure communications, without any additional conventional cryptographic systems, while utilizing the properties of the photons. Considerable research efforts have been invested to develop an efficient quantum key distribution (QKD) scheme over either free-space optical or fiber-optics channels. Most of these research efforts have been focused on a two-dimensional QKD, commonly realized by the use of the polarization state of photons. However, the data rates for the quantum key exchange in two-dimensional QKD are still low, while transmission distance is limited. On the other hand, it is well known that photons can carry both the spin angular momentum (SAM) and the orbital angular momentum (OAM), associated with the polarization and azimuthal phase of the complex electric field, respectively. Accordingly, we can define the combined-OAM-SAM state of a photon as |l, σ〉, where l and σ correspond to OAM and SAM indexes, respectively. Since the OAM eigenstates are orthogonal, an arbitrary number of bits per single photon can be transmitted, which could considerably increase the total secure bit rate. To improve secure data rates, we propose two types of protocols, namely, nonentangled-based (such as weak coherent state) and entanglement-assisted protocols, both employing the photon combined-OAM-SAM state, which can be used for secure key distribution over free-space optical and few-mode fiber channels. Two types of entanglement-assisted protocols are described, namely, two-basis and (D + 1)-basis protocols ( D is dimensionality of corresponding Hilbert space). We further describe how to implement the qudit gates required for implementation of these protocols. Finally, we discuss the security issues of the proposed protocols and determine both infinite and finite secret key fraction rates.

In-plane focusing of terahertz surface waves on a gradient index metamaterial film

We designed and implemented a gradient index metasurface for in-plane focusing of confined terahertz (THz) surface waves. We measured the spatial propagation of the surface waves by two-dimensional mapping of the complex electric field using a THz near-field spectroscope. The surface waves were focused to a diameter of 500 μm after a focal length of approximately 2 mm. In the focus, we measured a field amplitude enhancement of a factor of 3.

Characterisation of a symmetric AGATA detector using the [formula omitted] imaging scanning technique

The imaging scanning technique for the characterisation of large volume, highly segmented, HPGe detectors is demonstrated by comparing the measured spatial response of a symmetric AGATA crystal versus the theoretical calculations obtained with the Multi-Geometry Simulation (MGS) code. The signal rise-times measured as a function of the gamma-ray interaction positions, in both coaxial and planar regions of the detection volume, are presented and confronted with the expected behaviour obtained via MGS. The transition in charge carrier transport behaviour as a function of the depth is studied for the region of the complex electric field. In general, a fairly good agreement between theory and experiment is obtained. Only systematic deviations between simulation and measurement are observed in the critical front part of the AGATA detector. They may be ascribed to a non-linear impurity concentration profile of the germanium crystal.

BiotecVisions 2012, October

BiotecVisions 2012, October

GPU accelerated electric field Monte Carlo simulation of light propagation in turbid media using a finite-size beam model

An electric field Monte Carlo (EMC) simulation directly traces the complex electric field vectors in multiple scattering and estimates the electric field in a preferred direction. The full vectorial nature of EMC makes it a powerful and flexible tool to simulate the coherence and polarization phenomena of light. As a numerical method, EMC needs to launch a large number of photons to achieve an accurate result, making it time-consuming. Previously, EMC did not account for the beam size. Because of the stochastic character of the instantaneous electric field in the simulation, the convolution method alone is unsuitable for the Monte Carlo simulation of photon energy for a beam with a finite size. It is necessary to launch photons from all possible locations to simulate a finite-size beam, which results in a significant increase in the computational burden. In order to accelerate the simulation, a parallel implementation of the electric field Monte Carlo simulation based on the compute unified device architecture (CUDA) running on a graphics processing unit (GPU) is presented in this paper. Our program, which is optimized for Fermi architecture, is able to simulate the coherence phenomenon of a finite-size beam normally incident on turbid media. A maximum speedup of over 370x is achieved with a GTX480 GPU, compared with that obtained using an Intel i3-2120 CPU.

Plasmon Scattering from Single Subwavelength Holes

We map the complex electric fields associated with the scattering of surface plasmon polaritons by single subwavelength holes of different sizes in thick gold films. We identify and quantify the different modes associated with this event, including a radial surface wave with an angularly isotropic amplitude. This wave is shown to arise from the out-of-plane electric dipole induced in the hole, and we quantify the corresponding polarizability, which is in excellent agreement with electromagnetic theory. Time-resolved measurements reveal a time delay of 38±18 fs between the surface plasmon polariton and the radial wave, which we attribute to the interaction with a broad hole resonance.

The Research of Air Purification under Complex Electric Fields

A set of experimental device is built，to research the air purification under high voltage and high frequency complex electric fields. The results show that the half time TH will drop while the initial concentration of the aerosol particles reduces in air conditioning room, under high voltage and high frequency complex electric fields only or under the joint action of high voltage and high frequency complex electric fields and the filter. Compared with high voltage and high frequency complex electric fields only，the half time TH is observably reduced when they work together. The time of indoor air purification of air conditioning is greatly shortened. While the initial concentration of the aerosol particles is same, the diameters of aerosol particles are larger; the half time TH is less. The aerosol particles easily removed and the time of air purification is shorter.

Ultrashort Optical Pulse Propagation in terms of Analytic Signal

We demonstrate that ultrashort optical pulses propagating in a nonlinear dispersive medium are naturally described through incorporation of analytic signal for the electric field. To this end a second-order nonlinear wave equation is first simplified using a unidirectional approximation. Then the analytic signal is introduced, and all nonresonant nonlinear terms are eliminated. The derived propagation equation accounts for arbitrary dispersion, resonant four-wave mixing processes, weak absorption, and arbitrary pulse duration. The model applies to the complex electric field and is independent of the slowly varying envelope approximation. Still the derived propagation equation posses universal structure of the generalized nonlinear Schrödinger equation (NSE). In particular, it can be solved numerically with only small changes of the standard split-step solver or more complicated spectral algorithms for NSE. We present exemplary numerical solutions describing supercontinuum generation with an ultrashort optical pulse.