Electron energy spectrum in the field-ionized plasma

In this article, the effect of ionization on the energy spectrum of electrons within the interaction of a laser pulse with hydrogen atoms is investigated using particle-in-cell simulation codes. The results show that the behaviour of electrons' energy distribution function in the field-ionized plasma, which occurred due to the field ionization, compared with that in the pre-plasma strongly depends on the pulse shape. For short rise-time pulses (here 30 fs), due to the rapid enhancement of laser electric field, ionization occurs quickly, and as a result, there is not much difference in the electron energy in both the media. However, for pulses with rise time of 40 fs, in the pre-plasma state, the electron population reaches higher energies compared with the field-ionized plasma state. The main reason for this difference is the nonlinear wave breaking that happens earlier due to density inhomogeneity in the field-ionized plasma. On the other hand, at longer rise-time pulses (here 60 and 70 fs), electrons achieve higher energies in the field-ionized plasma than those in the case of pre-plasma. In this case, because of density fluctuations in the field-ionized plasma, the Raman backscattered radiations are seeded by a strong initial noise at the earlier times and the Mendonca condition for chaos threshold is met sooner. Therefore, the electrons gain more energy through the stochastic mechanism that is in agreement with chaotic nature of the motion.     

Dark solitons of the Biswas–Milovic equation by the first integral method

This paper studies the Biswas–Milovic equation that is a generalized version of the familiar nonlinear Schrodinger's equation describing the propagation of solitons through optical fibers for trans-continental and trans-oceanic distances with Kerr law nonlinearity by the aid of the first integral method. The dark 1-soliton solution is retrieved by the aid of this method and a couple of other singular periodic solutions are also obtained.     

Effect of the External Mirror Feedback Strength in the Dynamics and Spectrum of the Injected Semiconductor Lasers

We analytically investigate the effect of an external mirror on the stability of an injected semiconductor laser, the latter treated as injected damped oscillators. In the studied configuration, the injected semiconductor laser with an external mirror is under the influence of a chaotic oscillating optical signal that is generated by a similar semiconductor master laser. We derive our results in terms of the damping rate and resonance frequency. We show that the external mirror can eliminate the unstable modes of the injected laser at low frequencies. Furthermore, the mirror can enhance the damping of the oscillation modes of the injected semiconductor laser; consequently, the driven response of the injected laser may have a broad spectrum, even wider than that of the chaotic driving signal. We also show results for the bandwidths of the injection amplitude and phase increment as functions of the injection rate and feedback strength of the external mirror. In addition, we use bifurcation and time-series curves to describe the dynamical behavior of the injected laser. We identify the feedback strength of injected laser, relative to that of the master laser, which induces synchronization between the injected-laser oscillation modes and the master laser.     

Control of instability in a semiconductor laser using a functional pump current generator with a dynamical parameter

In this paper, an electric circuit to control the dynamic output of a semiconductor laser is introduced. The circuit controls chaos and instability of the laser output by changing its pumping current. The change of the current is also introduced by a nonlinear map. The most important element of this nonlinear map is a dynamical variable parameter. We have studied the dynamic behavior of the laser before and after applying the control using bifurcation curves and time series. We have shown that the laser output, in the intervals of the feedback phase and strength where it is chaotic, can be totally inverted to the quasi periodic (QP) and period one (P1) oscillation modes, by control method.     

One-dimensional mercury(II) coordination polymers with a flexible bidentate Schiff base ligand (Me2N-Ba)2Bn: Synthesis, characterization, and crystal structures

Three one-dimensional mercury(II) complexes, [Hg₂(μ_N,N-((Me₂N-Ba)₂Bn)(μ-X)₂X₂] _n , where X = Cl (I), Br (II), and I (III), (Me₂N-Ba)₂Bn = N,N′-bis(dimethylaminobenzylidene)butane-1,4-diamine, involving a bidentate Schiff base with a flexible spacer (=N-C-C-C-C-N=) were prepared under mild condition and characterized by elemental analyses (CHN), FT-IR, ¹H & ¹³C-NMR spectroscopy. The crystal structure of II has been determined by X-ray single-crystal diffraction. Each Hg(II) center adopts a distorted [HgNBr₃] tetrahedron environment arising from two crystallographically equivalent (Me₂N-Ba)₂Bn Schiff base ligands. Each of ligands acts as N₂-bis-chelating ligand with the nitrogen atoms of two imine functions in anti-form leading to the dinuclear [Hg₂(μ_N,N-(Me₂N-Ba)₂Bn)Br₂] groups. Such dinuclear [Hg₂(μ_N,N-((Me₂Nvg-Ba)₂Bn)Br₂] groups are bridged two iodine anions (μ-Br)₂ to form a neutral 1D-chain mercury (II) coordination polymer.     

Experimental Investigation of Natural Convection in Inclined Channel in Presence of Electrostatic Field

The influence of external electrohydrodynamic forces on natural convection from a flat plate has been studied. Temperature distribution in the aforementioned channel at α = 45°, 90°, and 150° angles in different 10-, 12-, and 15-kV electrostatic fields has been reviewed. Corona wind and the shape of the created vortex by electrohydrodynamics were detected. The results showed that heat transfer was enhanced by increasing the electrostatic field in all angles. In the presence of the field, enhancement of heat transfer of the plate at acute angles is better than for obtuse ones. The optimal angle in terms of heat transfer was 45°, noting heat transfer improvement by 61%.