Self-focusing Of Beam Research Articles

Second Harmonic Generation of High Power Cosh-Gaussian Beam in Thermal Quantum Plasma: Effect of Relativistic and Ponderomotive Nonlinearity

Second harmonic generation (SHG) of high power Cosh-Gaussian(ChG) beam in thermal quantum plasma (TQP) is explored in current investigation. Relativistic and ponderomotive nonlinearities are taken together in present investigation. Combination of relativistic-ponderomotive nonlinearities causes modification in electron mass, thereby producing density gradients inside plasma. This further produces self-focusing of main beam. The well-known WKB and paraxial approaches are used for solving main beam’s wave equation and to obtain 2nd order ordinary differential equation (ODE). There is generation of electron plasma wave (EPW) due to these density gradients. Excited EPW interacts with main beam to generate 2nd harmonics in plasma. Effects of combined relativistic-ponderomotive nonlinearities and established laser - plasma parameters on beam’s waist and SHG yield are studied in present study.

Dose increment in ultrashort particle irradiations via coherent stopping power

We present a relativistic self-consistent theory of the coherent stopping power (CSP) of ultradense charged particle beams propagating in a dense matter. CSP corresponds to a collective inelastic collision which adds to the ordinary stopping power of individual particles. Unlike the latter, which depends only on the particles' energy, CSP depends upon many more parameters such as the total charge of the ensemble and its charge density and shape. This paves the way for a broad variety of novel methods to tailor particle absorption and penetration in a dense matter. CSP losses can be explained both by collective excitations of single or multiple molecules and by the emission of coherent Cherenkov radiation. Here we demonstrate that the former mechanism is more relevant than the latter. We find that the coherent energy absorption of subpicosecond particle bunches in water occurs exciting a broad Debye process in the GHz range and an intermolecular stretching vibration mode in the THz region. We generalize the Bethe-Bloch stopping power formula to coherent effects including self-forces, dielectric screening, and absorption by the dense matter. For the sake of a self-consistent dynamical theory including phase space evolution, we have also generalized the Fermi-Eyges theory of particle diffusion to the presence of forces. Nonlinear dynamics is demonstrated, inducing nonlinear dose release, beam self-focusing, and self-enhancement of coherent losses. Given the advent of ultraintense particle sources and their use for biomedical and other relevant applications, our results may be of paramount importance for contemporary and future developments of science and technology. Published by the American Physical Society 2024

Self-focusing of high power q-Gaussian laser beam in collisional magnetized plasma

Self-focusing of high power q-Gaussian laser beam in collisional magnetized plasma

Radiation force of a self-focused vortex beam on Rayleigh particles

The radiation force of a partially coherent self-focusing vortex beam on Rayleigh particles is studied in this paper. According to the generalized Huygens-Fresnel principle and Rayleigh scattering theory, the effects of two main parameters of the beam, namely relative coherence length and non-trivial phase factor, on the self-focusing characteristics and radiation force are respectively researched. We have also conducted a brief analysis of the stability of particle capture using this self-focusing vortex beam. It has been found that changing the values of such parameters can flexibly regulate the self-focusing effect of the beam on propagation so as to effectively adjust the magnitude of the radiation force and trapping range. The results show that such beams can be used to trap and manipulate particles without using a focusing lens. In addition, this beam is able to capture two different refractive index particles, that is, high refractive index particles are captured near the focus, and low refractive index particles are captured on the z-axis. The research results establish a theoretical basis for the application of this novel partially coherent self-focusing vortex beams in optical tweezers technology.

Influence of Self-Focused Elliptical Laser Beam on Second Harmonic Generation in Cold Quantum Plasma

Influence of Self-Focused Elliptical Laser Beam on Second Harmonic Generation in Cold Quantum Plasma

Investigation of self-focusing of Gaussian laser beams within magnetized plasma via source-dependent expansion method

Self-focusing emerges as a nonlinear optical phenomenon resulting from an intense laser field and plasma interaction. This study investigates the self-focusing behavior of Gaussian laser beams within magnetized plasma environments utilizing a novel approach, source-dependent expansion. By employing source-dependent expansion, we explore the intricate dynamics of laser beam propagation, considering the influence of plasma density and external magnetic fields. The interplay between the beam's Gaussian profile and the self-focusing mechanism through rigorous mathematical analysis and numerical simulations, particularly in the presence of plasma-induced nonlinearities, is elucidated here. Our findings reveal crucial insight into the evolution of laser beams under diverse parameters, including the ponderomotive force, relativistic factors, plasma frequency, polarization states, external magnetic field, wavelength, and laser intensity. This research not only contributes to advancing our fundamental understanding of laser–plasma interactions but also holds promise for optimizing laser-driven applications.

Self-focusing morphology of juxtaposed double-ring Airyprime-Gaussian beam arrays

In this paper, the variation of self-focusing morphology and focusing interval of a juxtaposed double-ring Airyprime-Gaussian beam array (JDAPGBA) is investigated by changing the proportionality coefficient between the transverse displacements of the outer and the inner rings β. When β increases within a certain range, the JDAPGBA will change from a single self-focusing to the first self-focusing from the inner ring and the second self-focusing from the outer ring, accompanied by the gradual increase of the focusing interval. As β increases, the self-focusing ability of the inner ring is initially weaker than that of the outer ring, and then the self-focusing ability of the inner ring increases. In contrast, the self-focusing ability of the outer ring weakens until the two self-focusing skills are equal to each other. The generation of the double self-focusings of the JDAPGBA is explained in terms of the physical mechanism. In addition, the effects of the transverse displacement of the inner ring din and the distribution factor g on the focusing interval of the JDAPGBA are analyzed in detail. If din increases, the focusing interval also increases, both self-focusing abilities enhance, and the modulation range of β decreases as well. If the distribution factor g increases, the focusing interval rises, both self-focusing abilities weaken, the modulation range of β increases as well. Finally, the correctness of the above conclusions is confirmed by the experimental measurements of the self-focusing properties of the JDAPGBA. The above research provides a new scheme on how to generate double self-focusings and freely change the focusing interval, as well as new insights into the practical application of juxtaposed double-ring self-focusing beam arrays.

A hybrid variational method for beam propagation and interaction in a graded-index nonlinear waveguide

The hybrid variational method can be used to simplify multidimensional numerical simulations. We examine the applicability of this method to study the nonlinear propagation of a single beam and the interference of two spatial soliton beams in a graded-index optical waveguide governed by a two-dimensional nonlinear Schrodinger equation. We classified three distinct regimes of the dynamics that emerge during single Gaussian beam propagation, corresponding to beam decay, breather formation, and self-focusing. When two spatial soliton beams were set up to interfere in the waveguide, we identified the boundary where the nonlinear interaction during the interference led to excitation or self-focusing. These quite involved dynamics were used to test the predictive power of our variational models by comparing them with direct numerical simulations, obtaining good agreement.

Dominance of polarization modes and external magnetic field on self-focusing of laser beams in collisionless magnetized plasma

Dominance of polarization modes and external magnetic field on self-focusing of laser beams in collisionless magnetized plasma

Influence of Self-Focused Elliptical Laser Beam on Second Harmonic Generation in Cold Quantum Plasma

Influence of Self-Focused Elliptical Laser Beam on Second Harmonic Generation in Cold Quantum Plasma

Effect of the Contribution of the Local and Nonlocal Optical Response of an Isotropic Gyrotropic Medium on the Components of the Minkowski Energy–Momentum Tensor of the Electromagnetic Field of the Self-Focusing Beam

Effect of the Contribution of the Local and Nonlocal Optical Response of an Isotropic Gyrotropic Medium on the Components of the Minkowski Energy–Momentum Tensor of the Electromagnetic Field of the Self-Focusing Beam

Anisotropic atmospheric turbulence and partially coherent self-focusing vortex beams for wireless optical communication

It is generally believed that employing partially coherent light for wireless optical communication can improve the communication performance. In this paper, we show that whether the partial coherence contributes positively or negatively depends on the turbulence strength of the link. For illustration, partially coherent self-focusing vortex (PCSFV) beams propagating via anisotropic atmospheric turbulence at different altitudes are investigated. It is shown that lower coherence improves focusing and helps the signal receiving only for low-altitude and strong turbulence. There is an altitude related to the critical turbulence strength of the turbulence at which the communication performance is almost independent of the initial coherence of the beam. Besides, we focus on the channel capacity as well as the bit error rate (BER) for a high-altitude link. The results show that stronger anisotropy and larger inner scale parameters lead to higher average channel capacity with lower BER. By adjusting the beam waist or receiving aperture size, the communication performance can be further maximized. Our study represents the pioneering effort to assess the different impacts of the initial partial coherence on the receiving probability and validate the potential applications of PCSFV beams in wireless optical communications.

The self-focusing of hollow gaussian laser beam in magnetized plasma with transverse magnetic field by operating relativistic nonlinearity

The self-focusing of hollow gaussian laser beam in magnetized plasma with transverse magnetic field by operating relativistic nonlinearity

Self focusing of q-Gaussian laser beams in collisional plasma with axial density ramp: effect of Ohmic heating

Self focusing of q-Gaussian laser beams in collisional plasma with axial density ramp: effect of Ohmic heating

Dominance of polarization modes and absorption on self-focusing of laser beams in collisionless magnetized plasma

This work investigates the polarization modes i.e., Extraordinary (E-mode) and Ordinary (O-mode) on self-focusing of higher-order mode of elegant Hermite-cosh-Gaussian (EHChG) laser beams within collisionless magnetized plasma medium. In this study, the authors have taken transverse electromagnetic ([Formula: see text]) mode with mode indices (0, 4) and explored. The ponderomotive force is primarily responsible for the dielectric constant’s nonlinearity in this context. Also, WKB and paraxial approximations via the parabolic wave equation approach are used to establish the general form of differential equations for beam-width parameters in both transverse dimensions of the beam. In this paper, the authors have theoretically investigated the dominance of polarization modes and absorption coefficient on self-focusing. The final results show good enhancement of laser propagation through collisionless plasma medium.

Focal cone high harmonic generation driven by a 400 TW laser

The generation of self-focusing beams of extreme ultraviolet (XUV) radiation using the focal cone high harmonic generation (FCHHG) technique is examined for high energy lasers. The FCHHG geometry is created by passing a focusing laser beam through a gas sheet prior to reaching focus and thus creating a converging beam of high harmonic radiation. This leads to a larger interaction area that increases the total area of XUV emission while not exceeding the saturation intensity of the target atoms or increasing the density of the atoms. Such a method allows for scaling of HHG to any incident laser power. An experiment was conducted demonstrating such scaling to incident 400 TW pulses, showing both the expected spectral signature of HHG and the converging cone of XUV radiation. It was found that this technique is very sensitive to spatial non-uniformity in the driving laser, which has become more prevalent in high energy laser systems.

Laser Beam Self-Focusing in Silicon at an Absorbed Wavelength by a Vortex Beam in the Same Wavelength.

In this research, we present a novel approach to achieving super-resolution in silicon using the plasma dispersion effect (PDE) that temporarily controls the complex refractive index of matter. By employing a laser vortex pump beam, which is absorbed in the silicon, we can shape the complex refractive index as a gradient index (GRIN) lens, enabling the focusing of a laser probe beam within the material. Our study introduces a single beam at a wavelength of 775 nm for both the pump and the probe beams, offering tunable focusing capabilities and the potential to attain higher spatial resolution. These findings hold significant promise for applications in nanoelectronics and integrated circuit failure analysis, paving the way for advanced semiconductor imaging and analysis techniques.

Realization of double uniform line self-focusing of elliptical Airyprime beams

Double line self-focusing characteristics of elliptical Airyprime beams (EAPBs) with different elliptical vertical-axis factor β are investigated by varying the main ring radius r0. Overly large or small r0 results in the inhomogeneous distribution of light intensity at one linear focus of the double line self-focusing. Only when r0 is appropriate and β is within a certain range, can double uniform line self-focusing happen to the EAPB. Moreover, the self-focusing ability of the second line self-focusing is weaken than that of the first line self-focusing. Under the premise of our selected values of beam parameters, the EAPB can achieve double uniform line self-focusing when r0 = 0.3 mm and β = 0.58∼0.71. The focal length of the first line self-focusing, the lengths of double linear focus, and the self-focusing abilities of the double uniform line self-focusing can be regulated by varying β within the range of 0.58∼0.71. If β is smaller than 0.58 or larger than 0.71, it will lead to nonuniform line self-focusing. An explanation of the physical mechanism behind the double uniform line self-focusing of the EAPB is proposed. Finally, the experimental measurements of the line self-focusing of the EAPB confirm the validity of the above conclusions. This research provides a new solution on how to generate double uniform line self-focusing and new insights into the practical application of elliptical self-focusing beams.

Effect of self-focusing of bessel gauss laser beam on excitation of electron plasma wave in collisionless plasma with axial density ramp

Effect of self-focusing of bessel gauss laser beam on excitation of electron plasma wave in collisionless plasma with axial density ramp

Self-focusing of dark hollow Gaussian laser beams in cubic–quintic nonlinear media

Self-focusing of dark hollow Gaussian laser beams in cubic–quintic nonlinear media