Normalized Distance Of Propagation Research Articles

Influence of Magnetic field and Decentred Parameter on Self-Focusing of CoshGaussian Laser Beam in Collisional Magnetized Plasma

In the present investigation, Three-dimensional Cosh-Gaussian laser beam is introduced. The self-focusing and defocusing of Cosh-Gaussian laser beam in collisional magnetized plasma have been investigated theoretically. The final Differential equation for the beam width parameter is derived by following Wentzel-Kramer’s-Brillouin (WKB) and paraxial approximation through standard Akhmanov`s parabolic wave equation. The final results of numerical computation are presented in the plot of beam width parameters (f1 & f2) versus normalized propagation distance ( ). In present investigation the author shows nonlinear effect due to magnetic field (B0), decentered parameter (b) and plasma density on self-focusing and defocusing in collisional magnetized plasma. The results show well enhancement in beam of self-focusing.

Influence of self-focused high power Cosh-Gaussian beam on second harmonic generation in cold quantum plasma

The objective of present work is to investigate influence of self-focused high power Cosh-Gaussian (ChG) beam on second harmonic generation (SHG) in cold quantum plasma (CQP). WKB and Paraxial approximations are utilized for acquiring 2nd order differential equation representing propagation characteristics of ChG beam with normalized propagation distance. The modification in dielectric function of plasma is observed on account of relativistic nonlinearity causing self-focusing of ChG beam. The density gradients are produced in transverse direction. These density gradients cause electron plasma wave (EPW) excitation at main wave frequency. Further, the nonlinear interaction between pump wave and excited EPW produces 2nd harmonics in plasma. We have performed numerical simulations for exploring impact of various laser & plasma parameters on beam waist of ChG beam and conversion efficiency of 2nd harmonics. We have also made the comparison of given work with classical relativistic plasma (CRP) regime.

Interference enhancement effect in a single Airyprime beam propagating in free space.

An analytical expression of a single Airyprime beam propagating in free space is derived. Upon propagation in free space, a single Airyprime beam in arbitrary transverse direction is the coherent superposition of the Airyprime and the Airy-related modes, which results in the interference enhancement effect under the appropriate condition. The Airy-related mode is the conventional propagating Airy mode with an additional π/2 phase shift and a weight coefficient of half the normalized propagation distance. Due to the peak light intensity in the initial plane being set to be 1, the strength of interference enhancement effect is characterized by the maximum light intensity. The maximum light intensity of a single Airyprime beam propagating in free space is independent of the scaling factor and is only decided by the exponential decay factor. When the exponential decay factor is above the saturated value, the interference enhancement effect disappears. When the exponential decay factor decreases from the saturated value, the maximum light intensity of a single propagating Airyprime beam increases, and the position of maximum light intensity is getting farther away. With the increase of the scaling factor, the position of maximum light intensity of a single propagating Airyprime beam is extended. The intensity distribution and the transverse Poynting vector of a single propagating Airyprime beam are demonstrated in different observation planes of free space. The flow direction of transverse energy flux effectively supports the interference enhancement effect of a single propagating Airyprime beam. The Airyprime beam is experimentally generated, and the interference enhancement effect is experimentally confirmed. The interference enhancement effect is conducive to the practical application of a single Airyprime beam.

Non-linear interaction of Cosh-Gaussian beam in thermal quantum plasma under combined influence of relativistic-ponderomotive force

Non-linear interaction of Cosh-Gaussian beam in thermal quantum plasma (TQP) under combined influence of relativistic-ponderomotive force (RP Force) is explored. The authors have made use of parabolic equation approach for obtaining 2nd order differential equation governing behavior of beam waist of laser beam against normalized propagation distance through WKB and paraxial theory approaches. RK4 method is utilized for carrying out numerical simulations of this differential equation. Well established laser plasma parameters are taken for investigating response of beam waist with normalized distance. The comparison of present results is made with simple quantum plasma and relativistic plasma cases.

Physical meaning of the deviation scale under arbitrary turbulence strengths of optical orbital angular momentum.

The recently so-called deviation scale [Phys. Rev. A99, 013828 (2019)PLRAAN1050-294710.1103/PhysRevA.99.013828] bridges the connection between the result of the infinitesimal propagation equation (IPE) prediction and that of the single phase screen (SPS) approximation. Thanks to the multiple phase screen (MPS) approach, in this paper we elaborate the physical meaning of the deviation scale: the spatial accumulation of slight intensity modulation of incident orbital angular momentum (OAM)-carrying beam splits the original vortex into multiple individual vortices with a topological charge (TC) of +1 and regenerates the vortex-antivortex pairs with a TC of +1 and with a TC of -1, leading to a significant deviation between these two different results only when the disruption of this compound effect on the phase distribution of the incident OAM-carrying beam becomes more significant. Other than that, we also show that the appearance of the deviation scale cannot be predicted only by the Rytov variance, which can be predicted through the vortex-splitting ratio of the received optical field alone or with the help of the normalized propagation distance.

Third Harmonic Generation of Hermite-cosh-Gaussian laser Beam

In present study we have investigated the third harmonic generation (THG) of self-focused Hermite-cosh-Gaussian (HchG) laser beam, propagating through plasma. When intense short pulse laser propagates through plasma results ponderomotive force on electrons due to which electrons move away from the axial region, creating a low density plasma region. Due to electrostatic force, electrons gain oscillatory velocity and results density perturbation. Density oscillations at frequency 2ω1 couple with oscillatory velocity of electrons, at the fundamental frequency of incident laser result THG. Due to phase mismatch with the incident pulse, the third harmonic pulse is of smaller amplitude. Wiggler field satisfy the resonance condition by providing additional momentum to the photon of third harmonic pulse and this result increase in the normalized amplitude of third harmonic pulse. In the present study the study of beam width parameter with normalized propagation distance at optimum values of different laser parameters has been studied. We derived the coupled differential equation for the normalized amplitude, A'30/A 10, of third harmonic pulse. We analysed the efficiency of third harmonic pulse with ξ at optimum values of normalized intensity of fundamental laser.

Self-focusing of pseudo-nondiffracting laser beams with circular symmetry in collisional plasma under two ramp density profiles

The self-focusing of zeroth-order Bessel–Gaussian beams through plasma under exponential and tangential ramp density profiles is investigated theoretically by using Wentzel–Kramers–Brillouin approximation. To examine the effect of plasma density ramp on self-focusing of the studied beams, the evolution of beam-width parameter with normalized propagation distance is reported for diverse laser beams and plasma parameters. The results reveal that stronger self-focusing is obtained with exponential ramp density profile as compared to the tangential density ramp one.

Early and strong relativistic self-Focusing of cosh-Gaussian laser beam in cold quantum plasma

Relativistic self-focusing of cosh-Gaussian laser beam in the cold quantum plasma has been investigated theoretically. For a decentered parameter b=0.9, we present a comparative analysis for self-focusing of cosh-Gaussian laser beam in relativistic cold quantum (RCQ) and classical relativistic (CR) case. It is observed that as the beam penetrates deeper inside the RCQ plasma, the self-focusing ability of the laser beam enhances and shifted towards lower value of normalized propagation distance due to quantum contribution. The beam width parameter as a function of normalized propagation distance for various values of relative density parameter of the medium and intensity parameter has also been studied. The self-focusing is observed to be stronger with the increase in relative density parameter. Observation of early and strong self-focusing for higher values of relative density parameter and intensity parameter are reported. The present study might be very useful in the applications like the generation of inertial fusion energy driven by lasers, laser driven accelerators, scribing type of applications in electronics etc.

Nonlinear propagation of Gaussian laser beam in an inhomogeneous plasma under plasma density ramp

Nonlinear propagation of Gaussian laser beam in an inhomogeneous plasma under plasma density ramp is studied. The differential equation for beam width parameter is derived by parabolic wave equation approach under paraxial approximation. For different values of plasma density, laser intensity and initial beam width, the behavior of beam width parameter with the normalized propagation distance is examined. It is found that the beam width parameter decreases with a higher rate. The frequency of the oscillations increases while amplitude decreases and the laser beam focuses up to long distance. Further, increase in relative plasma density causes reduction in the amplitude of spot size of laser beam near the propagation axis.

Characteristics of Self-Focusing of a Gaussian Laser Pulse Under Lateral and Axial Plasma Density Variations

In this paper, we present a paraxial description of relativistic self-focusing of a Gaussian laser beam in a plasma channel with the density distribution as a function of radial and axial variations. We have derived the nonlinear dielectric permittivity of plasma due to ponderomotive force and relativistic effects. The effect of different conditions of the inhomogeneous plasma and the laser pulse on self-focusing and defocusing of Gaussian laser beam propagation in the plasma is studied. We find that with an increase in the value of intensity of the beam, self-focusing enhances and shifts toward lower values of normalized propagation distance. The self-focusing length also increases with an increase in channel width. When the density rapidly increases along the propagation distance, the nonlinearity increases and gives self-focusing at shorter values of $z$ .

Enhanced relativistic self-focusing of Hermite-cosh-Gaussian laser beam in plasma under density transition

Enhanced and early relativistic self-focusing of Hermite-cosh-Gaussian (HChG) beam in the plasmas under density transition has been investigated theoretically using Wentzel-Kramers-Brillouin and paraxial ray approximation for mode indices m=0, 1, and 2. The variation of beam width parameter with normalized propagation distance for m=0, 1, and 2 is reported, and it is observed that strong self-focusing occurs as the HChG beam propagates deeper inside the nonlinear medium as spot size shrinks due to highly dense plasmas and the results are presented graphically. A comparative study between self-focusing of HChG beam in the presence and absence of plasmas density transition is reported. The dependency of beam width parameter on the normalized propagation distance for different values of decentered parameter “b” has also been presented graphically. For m=0 and 1, strong self-focusing is reported for b=1.8, and for m=2 and b=1.8, beam gets diffracted. The results obtained indicate the dependency of the self-focusing of the HChG beam on the selected values of decentered parameter. Moreover, proper selection of decentered parameter results strong self-focusing of HChG beam. Stronger self-focusing of laser beam is observed due to the presence of plasma density transition which might be very useful in the applications like the generation of inertial fusion energy driven by lasers, laser driven accelerators, etc.

Sensitiveness of Decentered Parameter for Relativistic Self-Focusing of Hermite-cosh-Gaussian Laser Beam in Plasma

Sensitiveness of the decentered parameter for relativistic self-focusing of Hermite-cosh-Gaussian beam in the plasma is investigated theoretically using Wentzel-Kramers-Brillouin and paraxial ray approximation for mode indices 0, 1, and 2. The plot between the beam width parameter and the normalized propagation distance for different values of the decentered parameter and intensity has been reported and results obtained indicate the dependency of the self-focusing of the laser beam on the decentered parameter. The selection of the decentered parameter is more sensitive to self-focusing. For the mode indices ${\rm m}={0}$ and 1, self-focusing becomes stronger and for ${\rm m}={2}$ , self-focusing becomes weaker as the diffraction term becomes more dominant. Our emphasis is on the selection of the decentered parameter at which stronger self-focusing of laser beam is observed which might be very useful in the applications, such as the generation of inertial fusion energy driven by lasers, laser driven accelerators, and so on.

SOLITON OPTICAL FIBERS SUPERCONTINUUM GENERATION NEAR THE ZERO DISPERSION

During the last decade, the development of supercontinua (SC) sources has emerged as an interesting and active research field. This is largely due to new technological developments, which have allowed more controlled and accessible generation of supercontinua. In this paper we study the dynamics of Raman soliton during supercontinuum process when the pulse experiences initially normal group velocity dispersion with a negative dispersion. In this situation, the blue components of the spectrum form a Raman soliton moves faster than the input pulse because of Raman induced frequency downshifting ceases to occur as the spectrum of Raman soliton approaches the zero dispersion point. From this study one can distinguish that the first order bright soliton pulse depends on two important bases: first depends on the contents of the optical fibers and building method, where it is accomplished by making a balance between the dispersion effect and the nonlinear effect. The second depends on the parameters for mode and the starting point of the pulse shape inside the fiber such as the pulse width, normalized propagation distance and the existence of any nonlinear external effect.

Performance bounds for passive sensor arrays operating in a turbulent medium: plane-wave analysis.

The performance bounds of a passive acoustic array operating in a turbulent medium with fluctuations described by a von Kármán spectrum are investigated. This treatment considers a single, monochromatic, plane-wave source at near-normal incidence. A line-of-sight propagation path is assumed. The primary interests are in calculating the Cramer-Rao lower bounds of the azimuthal and elevational angles of arrival and in observing how these bounds change with the introduction of additional unknowns, such as the propagation distance, turbulence parameters, and signal-to-noise ratio. In both two and three dimensions, it is found that for large values of the index-of-refraction variance, the Cramer-Rao lower bounds of the angles of arrival increase significantly at large values of the normalized propagation distance. For small values of the index-of-refraction variance and normalized propagation distance, the signal-to-noise ratio is found to be the limiting factor. In the two-dimensional treatment, it is found that the estimate of the angle of arrival will decouple from the estimates of the other parameters with the appropriate choice of array geometry. In three dimensions, again with an appropriate choice of array geometry, the estimates of the azimuth and elevation will decouple from the estimates of the other parameters, but due to the constraints of the model, will remain coupled to one another.