super-Gaussian Laser Research Articles

Electrostatic wave assisted super-gaussian laser beam absorption in collisional plasma embedded with static magnetic field

Electrostatic wave assisted super-gaussian laser beam absorption in collisional plasma embedded with static magnetic field

Publisher Correction: Molecular alignment induced by a collision with the regulation of super-Gaussian laser pulse

Publisher Correction: Molecular alignment induced by a collision with the regulation of super-Gaussian laser pulse

Molecular alignment induced by a collision with the regulation of super-Gaussian laser pulse

Molecular alignment induced by a collision with the regulation of super-Gaussian laser pulse

Modulated super-Gaussian laser pulse to populate a dark rovibrational state of acetylene.

A pulse-shaping technique in the mid-infrared spectral range based on pulses with a super-Gaussian temporal profile is considered for laser control. We show a realistic and efficient path to the population of a dark rovibrational state in acetylene (C2H2). The laser-induced dynamics in C2H2 are simulated using fully experimental structural parameters. Indeed, the rotation-vibration energy structure, including anharmonicities, is defined by the global spectroscopic Hamiltonian for the ground electronic state of C2H2 built from the extensive high-resolution spectroscopy studies on the molecule, transition dipole moments from intensities, and the effects of the (inelastic) collisions that are parameterized from line broadenings using the relaxation matrix [A. Aerts, J. Vander Auwera, and N. Vaeck, J. Chem. Phys. 154, 144308 (2021)]. The approach, based on an effective Hamiltonian, outperforms today's abinitio computations both in terms of accuracy and computational cost for this class of molecules. With such accuracy, the Hamiltonian permits studying the inner mechanism of theoretical pulse shaping [A. Aerts et al., J. Chem. Phys. 156, 084302 (2022)] for laser quantum control. Here, the generated control pulse presents a number of interferences that take advantage of the control mechanism to populate the dark state. An experimental setup is proposed for in-laboratory investigation.

Exploring the Benefits of Ablation Grid Adaptation in 2D/3D Laser Ablation Inductively Coupled Plasma Mass Spectrometry Mapping through Geometrical Modeling.

This study aims to investigate the potential benefits of adapting the ablating grid in two-dimensional (2D) and three-dimensional (3D) laser ablation inductively coupled plasma mass spectrometry in a single pulse mapping mode. The goals include enhancing the accuracy of surface sampling of element distributions, improving the control of depth-related sampling, smoothing the post-ablation surface for layer-by-layer sampling, and increasing the image quality. To emulate the capabilities of currently unavailable laser ablation stages, a computational approach using geometrical modeling was employed to compound square or round experimentally obtained 3D crater profiles on variable orthogonal or hexagonal ablation grids. These grids were optimized by minimizing surface roughness as a function of average ablation depth, followed by simulating the post-ablation surface and related image quality. An online application (https://laicpms-apps.ki.si/webapps/home/) is available for users to virtually experiment with contracting/expanding orthogonal and hexagonal ablation grids for generic 3D super-Gaussian laser crater profiles, allowing for exploration of the resulting post-ablation surface layer roughness and depth.

Impact of wiggler magnetic field on wakefield generation and electron acceleration by Gaussian, Super-Gaussian, and Bessel-Gaussian laser pulses propagating in collisionless plasma – ERRATUM

Impact of wiggler magnetic field on wakefield generation and electron acceleration by Gaussian, Super-Gaussian, and Bessel-Gaussian laser pulses propagating in collisionless plasma – ERRATUM - Volume 89 Issue 2

Self-focusing and defocusing phenomena of super-Gaussian laser beams in plasmas carrying density gradient

Considering nonlinearities due to relativistic mass variation and ponderomotive force driven depression in the electron density, a model is developed for the self-focusing of a super-Gaussian laser beam in inhomogeneous plasmas. Since paraxial ray approximation is not appropriate for the beams of super-Gaussian profile, the formulation is developed based on the moment theory. To have an in-depth understanding of self-focusing and defocusing phenomena and to develop generalized treatment, three different types of plasma density profiles namely linear, tangent and exponential density profiles, are considered and the results are compared. Due to the saturating nature of nonlinear permittivity with laser intensity, the beam is found to undergo periodic focusing because of competition between the diffraction divergence and nonlinear self-focusing effects. The ponderomotive nonlinearity enhances the self-focusing. As the super-Gaussian beam moves into higher density plasma region up to several Rayleigh lengths, stronger self-focusing is achieved and the value of minimum spot size decreases.

Magnetic field-assisted wakefield generation and electron acceleration by Gaussian and super-Gaussian laser pulses in plasma

This study focuses on electron acceleration and wakefield produced by Gaussian and Super-Gaussian (SG) laser pulses through plasma medium in the attendance of an external magnetic field. Two shapes of different laser spatial profiles Gaussian and SG are considered. Besides, governing equations for analysis of laser wakefield and electron acceleration by using of hydrodynamics fluid equations, Maxwell’s equations and perturbation technique for Gaussian and SG laser pulses in weakly nonlinear regime have been derived. In addition, influence of the external magnetic field strengths, laser intensity, the pulselength, the plasma electron density and the laser frequency on the wakefield and the electron energy gain have been investigated. Numerical results indicate that by increasing of external magnetic field, the amplitude of wakefield increases. Moreover, it is observed that wakefield amplitude excited by SG laser pulse in comparison with Gaussian laser pulse is larger when external magnetic field is increased. Furthermore, it is found that wakefield amplitude and shape of wakefield generation in within homogeneous plasma greatly are related to the laser profile type, selected laser parameters and external magnetic field. In addition, it is seen that influence of external magnetic field, while laser intensity enhances, on the electron energy gain in SG and Gaussian laser pulses is insignificant.

Electron Bernstein wave aided heating of collisional nanocluster plasma by nonlinear interactions of two super-Gaussian laser beams

In this present theoretical study, we investigate electron Bernstein wave (EBW) aided collisional nanocluster plasma heating by nonlinear interaction of two super-Gaussian laser beams. The interactions of laser beams electric field profiles with electronic clouds of nanoclusters cause the beat wave. The nonlinear ponderomotive force is generated through the beat wave. There may be good potential to excite the EBW aiding cluster plasma to lead electron heating via cyclotron damping of the Bernstein wave. An analytical scheme is proposed for the anomalous heating and evolution of electron temperature by using this mechanism. Graphical discussions were promised to achieve extreme heating rate via the spatial shape of super-Gaussian laser beams and the resonance condition of beat wave to surface plasmon frequency. The heating is controlled by tuning the laser beam width, mode index, collisional frequency, clustered radius, and density.

Spatial evolution leading to multiple filament formation of higher order super Gaussian beam in bulk medium at input power P >>Pcr

Multiple filamentation in higher order super Gaussian laser beam propagating in chalcogenide glass is investigated by numerically solving nonlinear Schrödinger equation with split step beam propagation method at input power range of 40 – 160 Pcr and compared to the process in super Gaussian beam. The effect of raising the beam order on the deterministic nature of multiple filaments, threshold power of filamentation, length of filamentation and the number of filaments formed are analysed. The results indicate that within a range of beam order and input power, the process of multiple filamentation in super Gaussian beam may be controlled through beam order. The study further exemplifies the importance of deterministic filaments and the ‘role of beam order as a tool’ in control of self-guided laser beam properties in filamentation process.

Kerr lens effect induced by a super-Gaussian laser beam

Recently, a new type of laser cavity has been proposed. It includes two Diffractive Optical Elements set inside the resonator against the cavity mirrors in order to achieve the structuring of the fundamental mode. The latter is a perfect Gaussian beam (M2 = 1) from the output mirror side, and super-Gaussian in the amplifying medium. Such a special cavity allows for improving the energy extraction, and it should be interesting to mode-lock such a laser cavity by using the KLM technique. For that, we aim to model the Kerr lensing effect, induced by a super-Gaussian beam. An analytical expression for the Kerr focal length has been deduced from a Zernike polynomial development. The obtained results are in a good agreement with a diffraction analysis.

Electron Bernstein wave excitation by beating of two copropagating super-Gaussian laser beam in a collisional nanocluster plasma

An analytic formalism is developed to study electron Bernstein wave excitation by two copropagating high power super-Gaussian laser beams in a collisional nanocluster plasma. The medium is assumed to contain spherical plasma plume ball of nanocluster. As the electric field of two laser beams interact with nanoclustered plasma, it would cause the beat wave frequency ω=ω1−ω2. The laser beat wave exerts a nonlinear pondermotive force on electron cloud of clustered plasma that in turns lead to excite the electron Bernstein wave in the laser field polarizations direction. The effective finite y-component of the beat wave experiences group velocity and it might cause convective losses. The spatial shape of electron Bernstein wave normalized potential and power profile promises better excitation mechanism in nanoclustered plasma as compared to only plasma medium. It is observed that excitation is much enhanced when the laser beat frequency lies near the effective plasmons frequency of nanoclustered plasma. The excitation is detuned by varying the laser mode index, clustered radius, collisional frequency, parameter b. One may apply this theory of electron Bernstein wave excitation in toroidal fusion devices.

Terahertz radiation generation by a super-Gaussian laser pulse in a magnetized plasma

We investigate the enhanced terahertz (THz) field generation via transverse wakefield by a super-Gaussian laser pulse in a magnetized plasma. Due to the “hat-on-top” intensity profile, the super-Gaussian laser pulse may be better for excitation of nonlinearities in plasmas. We utilize the special properties of the super-Gaussian laser pulse to generate THz current in a magnetized plasma. The transverse wakefield is significantly higher for the super-Gaussian laser pulse in comparison to the Gaussian laser pulse. The magnetic field provides a resonance to focus the THz fields. The transverse current at THz frequency can also be controlled by adjusting the index of the super-Gaussian laser pulse. We report about ten-fold enhanced THz field from this mechanism by using the super-Gaussian laser pulse. We observe that the stable THz is generated with a maximum field strength of ∼1 GV/cm and a relatively broad spectrum extending out to 50 THz, which corresponds to the conversion efficiency in order of 10−2 for a magnetic field strength of 1 T. The efficiency of this process may be optimized and controlled by the laser and plasma parameters, which is of high interest for various applications such as THz extreme nonlinear optics.

Impact of hot electrons on optical excitation of terahertz radiation by beating of supergaussian lasers in electron-positron collisional plasma

The mechanism of generation of terahertz (THz) radiation with beating of two supergausssian lasers in corrugated density plasma containing hot electron-positron (e-p) is revisited. Resonance condition for optical excitation of THz emission is reported to be modified due to finite temperature of plasma species (electrons-positrons to the few order keV range) in the presence of weak collisions. The collision frequency is optimized to the range ν ≤ 0.5ω p in the e-p plasma depending on the temperature and collisional rates. The effect of electron temperature, collision frequency and suitability of supergaussian laser is investigated on phase modulation to achieve highest emitted THz field with 6% efficiency of the mechanism.

Tunable terahertz radiation generation using the beating of two super-Gaussian laser beams in the collisional nanocluster plasma

In this paper, generation of terahertz (THz) radiation by the beating of two super-Gaussian laser beams in a nanocluster plasma is investigated, theoretically. The electric field of laser beams interacts with the nanocluster, leads to the ionization of the cluster atoms, and produces nanoplasma. Interaction of laser beams with the electronic clouds of nanoplasma generates ponderomotive force that leads to the creation of a macroscopic electron current at the beat frequency, which can generate THz radiation. The THz wave equations and THz efficiency in the nanoplasma medium were analytically derived and then numerically discussed. The effects of the density and radius of nanoclusters, the laser beam width, and intensity of super-Gaussian lasers on the THz radiation efficiency have been investigated in the nanoplasma-based THz emitter. The results indicated when the beat-wave frequency approaches the effective plasmon frequency of the nanoplasma, the maximum value of the field amplitude of THz radiation is acquired. In addition, it was found that the best situation that can be obtained is the THz radiation occurring at frequency ω = ω p / 3 .

Terahertz emission during laser-plasma interaction: effect of electron temperature and collisions

The electron-neutral collisions in the plasma become crucial with regard to the generation of THz radiation when thermal motion of the electrons is considerable. If we look at the mechanism of THz emission, this is only the movement/oscillations of the electrons which is responsible for the excitation of nonlinear current that generated the THz radiation. The present work aims to disclose the role of thermal motion of the plasma electrons to the resonance condition and the THz emission when two co-propagating super-Gaussian laser beams beat in the plasma. The dynamics of the plasma electrons and subsequent generation of nonlinear current are discussed in greater detail for the emission of THz radiation.

Self-defocusing of super-Gaussian laser beam in tunnel ionized plasmas

Based on moment theory, an analytical formalism of high intensity super-Gaussian laser beam propagation through a tunnel ionized gas is developed by including the effects of diffraction divergence and nonlinear refraction. During the interaction of the laser with the plasma, the plasma density is found to have a broad maximum on the axis in the direction of propagation of the laser, causing self defocusing of the laser beam. It is seen that the super-Gaussian beam suffers stronger divergence than a Gaussian beam. The laser beam is found to get more defocused for the cases of higher intensity and smaller spot size of the laser. For in depth study, the calculations are carried out for argon, neon and xenon gases and it is seen that different gases lead to different diffraction divergence.

Self-focused amplitude modulated super Gaussian laser beam in plasma and THz radiation with high efficiency

Based on self- focusing of an amplitude modulated super Gaussian laser beam in preformed ripple density plasma, one scheme can be proposed for generating terahertz (THz) radiation at the modulation frequency when pondermotive nonlinearity is operative. The eikonal in paraxial ray approximation (PRA) along with higher order terms in the expansion of the dielectric function have been taken into account. Intensity variation in the direction transverse to the propagated laser causes a pondermotive force which generates transient transverse nonlinear current. At the modulation frequency, the mentioned current drives radiation in THz domain. Therefore, comparing to simple PRA, inclusion of terms with higher order enhances beam self-focusing, THz radiation field and, efficiency. In addition, the degree of the self-focusing is reduced in higher laser beam orders and has changed by the modulation index and the time. Here, by considering higher order paraxial ray approximation and optimizing laser beam and ripple density, plasma parameters are investigated and the efficiency of THz radiation reaches up to 6.5%. This method can be applied for the efficient types of THz radiation.

Relativistic self focusing and frequency shift of super-Gaussian laser beam in plasma

Relativistic self focusing and frequency shift of laser beam having super-Gaussian profile in space and Gaussian profile in time is studied in a plasma. The relativistic mass nonlinearity is found to cause time dependent self focusing of the laser pulse and the saturation effect of nonlinearity avoids point focusing of the beam. For ultrashort laser pulse, the front of the pulse undergoes frequency down shift while that of the tail undergoes up shift. Frequency shift increases and self focusing becomes stronger for higher intensity of the laser. The self focusing is also stronger for the laser beam carrying larger wavelength.

Role of magnetic field on self focusing of super-Gaussian laser beam under relativistic effect

Considering an external magnetic field along the direction of propagation of laser, the self focusing of a super-Gaussian laser beam is studied when it propagates through the plasma at relativistic intensities. We consider the cyclotron motion of the electrons and use the tensor form of the plasma dielectric constant obtained based on the direction of the external magnetic field. For completeness, relativistic mass effect is incorporated in both the plasma frequency and electron cyclotron frequency. Using appropriate conditions, an equation for the beam width parameter is derived and solved. The equilibrium beam radius for a self trapped laser beam is also derived. Self focusing is better when cyclotron effects are taken into account. At higher intensity and higher spot size of the laser beam, self focusing becomes better.