# Yousef I SalaminAmerican University of Sharjah | AUS

Yousef I Salamin

PhD

## About

119

Publications

17,935

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2,894

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Additional affiliations

September 2003 - present

September 2003 - November 2015

January 1988 - August 2003

**Birzeit University**

Position

- Professor

## Publications

Publications (119)

Relativistic spin-polarized electron beams are important for fundamental research and the industry, but their generation currently requires conventional accelerators or ultrastrong laser facilities, limiting their accessibility and broad applications. Here, we put forward a novel method for constructing a compact efficient "polarizer" that achieves...

Vortex γ photons, which carry large intrinsic orbital angular momenta (OAM), have significant applications in nuclear physics, atomic physics, hadron physics, high-energy particle physics, and astrophysics, but their production remains unclear. In this work, we investigate the generation of such photons from nonlinear Compton scattering of circular...

A two-parameter model for chirping the frequency of a plane-wave laser pulse is introduced using a binomial expansion. Acceleration of single electrons, through interaction with the plane-wave binomially chirped laser pulse, is investigated by solving the relativistic equations of motion, analytically and numerically. Multi-GeV energy gains are rep...

Compact spin-polarized positron accelerators play a major role in promoting significant positron application research, which typically require high acceleration gradients and polarization degree, both of which, however, are still great challenging. Here, we put forward a novel spin-polarized positron acceleration method which employs an ultrarelati...

Relativistic spin-polarized (SP) lepton beams are important for investigating spin-dependent interaction processes. In particular, spatially structured spin-polarized (SSP) lepton beams may find new applications in material, atomic, nuclear, high-energy physics and new physics beyond the Standard Model. However, realizing ultrafast generation and s...

Polarized attosecond γ−rays may offer excitation and hyperfine tracking of reactions relevant to nuclear physics, astrophysics, high-energy physics, etc. However, unfortunately, generation of a feasible and easy-to-deploy source is still a great challenge. Here, we put forward a novel method for producing ultra-collimated high-brilliance polarized...

High-brilliance circularly polarized γ-photon beams are of great significance for a wide range of applications. However, their generation through nonlinear Compton scattering must require a high-density longitudinally-spin-polarized electron beam and consequently is still a great challenge. Here, we put forward a novel method to generate such γ-pho...

Laser wakefield acceleration is paving the way for the next generation of electron accelerators, for their own sake and as radiation sources. A controllable dual-wake injection scheme is put forward here to generate an ultrashort triplet electron bunch with high brightness and high polarization, employing a radially polarized laser as a driver. We...

Vortex γ photons, which carry large intrinsic orbital angular momenta (OAM), have significant applications in nuclear, atomic, hadron, particle and astrophysics , but their production remains unclear. In this work, we investigate the generation of such photons from nonlinear Compton scattering of circularly polarized monochro-matic lasers on vortex...

Single-electron acceleration in vacuum by exponentially-chirped plane-wave and tightly-focused Gaussian laser pulses is investigated. Numerical simulations employing the chirped fields lead to GeV net energy gain from PW-class femtosecond laser pulses.

Single-electron acceleration in vacuum by exponentially-chirped plane-wave and tightly-focused Gaussian laser pulses is investigated. Numerical simulations employing the chirped fields lead to GeV net energy gain from PW-class femtosecond laser pulses.

The rapid development of ultrafast ultraintense laser technology continues to create opportunities for studying strong-field physics under extreme conditions. However, accurate determination of the spatial and temporal characteristics of a laser pulse is still a great challenge, especially when laser powers higher than hundreds of terawatts are inv...

An all-optical method of ultrafast spin rotation is put forward to precisely manipulate the polarization of relativistic charged particle beams of leptons or ions. Laser-driven dense ultrashort beams are manipulated via single-shot interaction with a copropagating temporally asymmetric laser pulse of moderate intensity. Using semiclassical numerica...

Rapid development of ultrafast ultraintense laser technologies continues to create opportunities for studying strong-field physics under extreme conditions. However, accurate determination of the spatial and temporal characteristics of a laser pulse is still a great challenge, especially when laser powers higher than hundreds of terawatts are invol...

Laser wakefield acceleration is paving the way for the next generation of electron accelerators, for their own sake and as radiation sources. A dual-wake injection scheme is put forward here to generate an ultrabrilliant polarized attosecond electron bunch, employing a radially polarized laser as a driver. We find that the laser-modulated fields in...

High-energy spin-polarized electron, positron, and \(\gamma\)-photon beams have many significant applications in the study of material properties, nuclear structure, particle physics, and high-energy astrophysics. Thus, efficient production of such polarized beams attracts a broad spectrum of research interests. This is driven mainly by the rapid a...

High-energy spin-polarized electron, positron, and γ-photon beams have many significant applications in the study of material properties, nuclear structure, particle physics, and high-energy astrophysics. Thus, efficient production of such polarized beams attracts a broad spectrum of research interests. This is driven mainly by the rapid advancemen...

An all-optical method of ultrafast spin rotation is put forward to precisely manipulate the polarization of relativistic charged particle beams of leptons or ions. In particular, laser-driven dense ultrashort beams are manipulated via single-shot interaction with a co-propagating moderate temporally asymmetric (frequency-chirped or subcycle THz) la...

Employing a two-parameter model for representing the radiation field, the theory of cosmic-ray acceleration by cyclotron autoresonance is analytically generalized here to include any state of polarization. The equations are derived rigorously and used to investigate the dynamics of the nuclides $_1$H$^1$, $_2$He$^4$, $_{26}$Fe$^{56}$, and $_{28}$Ni...

A two-parameter model for chirping the frequency of a plane-wave laser pulse is introduced using a binomial expansion. Acceleration of single electrons, through interaction with the plane-wave binomially chirped laser pulse, is investigated by solving the relativistic equations of motion, analytically and numerically. Multi-GeV energy gains are rep...

A Zevatron is an accelerator scheme envisaged to accelerate particles to ZeV energies (1 ZeV = 10 ²¹ eV). Schemes, most notably the internal shock model, have been proposed to explain the acceleration of ultra-high-energy cosmic-ray particles that have been sporadically detected reaching Earth since 1962. Here, the cyclotron auto-resonance accelera...

A Zevatron is an accelerator scheme envisaged to accelerate particles to ZeV energies (1 ZeV = $10^{21}$ eV). Schemes, most notably the internal shock model, have been proposed to explain the acceleration of ultra-high-energy cosmic-ray (UHECR) particles that have been sporadically detected reaching Earth since 1962. Here, the cyclotron auto-resona...

In laser-solid interactions, electrons may be generated and subsequently accelerated to energies of the order of magnitude of the ponderomotive limit, with the underlying process dominated by direct laser acceleration. The breaking of this limit, realized here by a radially polarized laser pulse incident upon a wire target, can be associated with s...

Generation of high-flux vortex $ \gamma $ γ -ray pulses is investigated in the interaction of ultraintense Bessel–Bessel laser bullets colliding head-on with ultrarelativistic electron bunches in the quantum radiation-dominated regime. In the simulations, a semiclassical Monte–Carlo method is used, based on the radiation probabilities in the local...

A Bessel-Bessel laser bullet is the ultra-short and tightly-focused analogue of a non-diffracting and non-dispersing laser Bessel beam. Analytic investigation of the energy, linear momentum, energy flux, and angular momentum, associated with the fields of a Bessel-Bessel bullet, propagating in an under-dense plasma, is conducted in this work. The a...

Three of the headings of Table 1, which have been switched by mistake in our paper, are corrected here. The rest of the paper, including all results and conclusions, remain intact.

In laser-solid interactions, electrons may be generated and subsequently accelerated to energies of the order-of-magnitude of the ponderomotive limit, with the underlying process dominated by direct laser acceleration. Breaking this limit, realized here by a radially-polarized laser pulse incident upon a wire target, can be associated with several...

A simple model is introduced for the fields of a chirped laser pulse. As an application, dynamics of laser-acceleration of a single electron by the fields of a pulse, with a sin4 envelope, is investigated. Multi-GeV energy gains from interaction with pulses of peak intensity I0~1020 W/cm2, are reported.

Encouraged by recent advances in radially-polarized laser technology, simulations have been performed of electron acceleration by a tightly-focused, ultra-short pulse in a parabolic plasma micro-channel. Milli-joule laser pulses, generated at kHz repetition rates, are shown to produce electron bunches of MeV energy, pC charge, low emittance and low...

Fields of a laser Bessel-Bessel bullet are presented, from solution to the wave equations of the scalar and vector potentials in the presence of an under-dense plasma. Propagation over many centimeters without distortion is demonstrated. © 2019 The Author(s)

Considerable theoretical and experimental work has lately been focused on waves localized in time and space. In optics, waves of that nature are often referred to as light bullets. The most fascinating feature of light bullets is their propagation without appreciable distortion by diffraction or dispersion. Here, analytic expressions for the fields...

Provided the intensity is not too high (for example, with I << 10¹⁸ W/cm², for a wavelength of 1 μm), response of an under-dense plasma to the fields of a laser pulse can still be considered linear, and inhomogeneous wave equations for the vector and scalar potentials A and Φ, respectively, may be derived from Maxwell’s equations. A rigorous, but a...

Analytic expressions for the fields of a radially polarized, ultrashort and tightly focused laser pulse propagating in a linear-response plasma are derived and discussed. The fields are obtained from solving the inhomogenous wave equations for the vector and scalar potentials, linked by the Lorenz gauge, in a plasma background. First the scalar pot...

Fully analytic expressions, for the electric and magnetic fields of an ultrashort and tightly focused laser pulse of the radially polarized category, are presented to lowest order of approximation. The fields are derived from scalar and vector potentials, along the lines of our earlier work for a similar pulse of the linearly polarized variety. A s...

Preface:
The International Conference Frontiers in Theoretical and Applied Physics |UAE 2017 was organized by the Department of Physics at the American University of Sharjah (AUS) in partnership with the Emirates Mars Mission and Mohammed Bin Rashid Space Center (MBRSC) in Dubai-United Arab Emirates. The conference was endorsed by the American Phys...

Analytic expressions for the electromagnetic fields of an ultrashort, tightly focused, linearly polarized laser pulse in vacuum are derived from scalar and vector potentials using a small parameter, which assumes a small bandwidth of the laser pulse. The derived fields are compared with those of the Lax series expansion and the complex-source-point...

Analytic expressions for the electric and magnetic fields of an ultrashort, tightly focused, linearly polarized laser pulse are derived, to lowest order of a truncated power-series expansion, from vector and scalar potentials. Clear steps are described for the analytic and numerical evaluation of higher-order terms in the series, to any desired acc...

Analytic expressions for the electric and magnetic fields of a radially polarized ultrashort and tightly focused laser pulse, propagating in vacuum, are derived from scalar and vector potentials satisfying simple initial conditions. It is shown that for a pulse of axial length comparable to a wavelength, only the zeroth (lowest-order) term in a pow...

A vacuum auto-resonance accelerator scheme for electrons, which employs terahertz radiation and currently available magnetic fields, is suggested. Based on numerical simulations, parameter values, which could make the scheme experimentally feasible, are identified and discussed.

Several aspects of the interaction of particle beams with ultrastrong laser fields are discussed. Firstly, we consider regimes when radiation reaction is not essential and it is demonstrated that employing chirped laser pulses, significant improvement of the direct acceleration of particles can be achieved. Results from single- and many-particle ca...

Theoretical investigations are presented, and their results are discussed, of
the laser acceleration of a single electron by a chirped pulse. Fields of the
pulse are modeled by simple plane-wave oscillations and a $\cos^2$ envelope.
The dynamics emerge from analytic and numerical solutions to the relativistic
Lorentz-Newton equations of motion of t...

Single MeV electrons subjected in vacuum to single high-intensity
quadratically-chirped laser pulses are shown to gain multi-GeV energies. The
laser pulses are modeled by finite-duration trapezoidal and $\cos^2$
pulse-shapes and the equations of motion are solved numerically. It is found
that, typically, the maximum energy gain from interaction wit...

Autoresonance laser acceleration of electrons is theoretically investigated
using circularly polarized focused Gaussian pulses. Many-particle simulations
demonstrate feasibility of creating over 10-GeV electron bunches of ultra-high
quality (relative energy spread of order 10^-4), suitable for fundamental
high-energy particle physics research. The...

According to the Lawson-Woodward theorem, an electron cannot gain
any energy from interaction with an ideal plane-wave laser pulse. We
demonstrate analytically and numerically that chirping the frequency of
the pulse distorts it in a sensitive way and leads to net energy gain by
an electron submitted to it.

Results from theoretical investigations are presented which show that protons can be accelerated from rest to a few hundred MeV by a 1-PW chirped radially polarized laser pulse of several hundred femtosecond duration and focused to a waist radius comparable to the radiation wavelength. Single-particle calculations are supported by many-particle and...

Detailed single- and many-particle calculations are carried out for the
acceleration of protons employing linearly-polarized plane-wave and
tightly-focused chirped laser pulses of several ten to several hundred
femtosecond durations, petawatt peak powers and relativistic peak
intensities of the order of 10^21-10^22 W/cm^2 [1,2]. Analytic and
numeri...

The dynamics of ion acceleration in tightly focused laser beams is investigated in relativistic simulations. Studies are performed to find the optimal parameters which maximize the energy gain, beam quality, and flux. The exit ionic kinetic energy and its uncertainty are improved and the number of accelerated particles is increased by orders of mag...

Interaction of a frequency-chirped laser pulse with single protons and a hydrogen gas target is studied analytically and by means of particle-in-cell simulations, respectively. The feasibility of generating ultraintense (10(7) particles per bunch) and phase-space collimated beams of protons (energy spread of about 1%) is demonstrated. Phase synchro...

Calculations show that 10 keV helium and carbon ions, injected midway between two identical 1 TW-power crossed laser beams of radial polarization, can be accelerated in vacuum to energies of utility in ion lithography. As examples, identical laser beams, crossed at 10° and focused to waist radii of 7.42mum, accelerate He2+ and C6+ ions to average k...

Two interfering ultra-high intensity laser beams of radial polarization are shown to accelerate protons, in vacuum, to several GeV. Both co-propagating and counter-propagating beams of slightly different frequencies and amplitudes are considered. The accelerated protons have energy gradients of several hundred GeV/m, less than 1% energy spread and...

Two constants of the motion, which simplify the relativistic particle dynamics in a laser beam of radial polarization, are identified. Many-particle simulations based on the reduced set of equations of motion in a beam of relativistic intensity, demonstrate acceleration in vacuum to GeV energies of electrons, alpha particles and oxygen bare nuclei....

Electrons and {alpha} particles injected midway between two ultrahigh intensity crossed laser beams of radial polarization are shown to be accelerated in vacuum to several gigaelectron volts and to have average energy gradients in excess of 150 GeV/m. A unique model of the crossing beams is suggested, which maximizes the particle energy gain and mi...

Fields of a linearly polarized fundamental Gaussian beam are derived exactly using the propagation characteristics of a complex-source-point spherical wave diverging from the origin. Intensity distributions are calculated and compared with their counterparts in a truncated series. It is found that utility of the exact fields is limited by a discont...

In this paper, the fields of a radially polarized fundamental Gaussian beam are derived with a complex-source-point spherical wave approach and then compared and contrasted with those derived recently from a Lax series to the order of ε15, where ε is the diffraction angle. It is shown that the domain of validity of the derived fields is restricted...

We investigate the relativistic dynamics of electrons in intense laser fields. Examples of both free and bound electron dynamics
are discussed using the approach appropriate for each particular case, i.e., either classical relativistic mechanics or relativistic
quantum mechanics. The algorithm for numerically solving the Dirac equation is explained...

An error, involving the last three terms in the truncated series giving the output power of a radially polarized laser system, has been detected and is corrected here.

An error involving the coefficients of the last three terms in the truncated series giving the output power of a radially polarized laser system has been detected and is corrected here.

Theoretical investigations show that linearly and radially polarized multiterawatt and petawatt laser beams, focused to subwavelength waist radii, can directly accelerate protons and carbon nuclei, over micron-size distances, to the energies required for hadron cancer therapy. Ions accelerated by radially polarized lasers have generally a more favo...

Fields of a radially polarized petawatt laser beam, represented by a truncated series in the diffraction angle epsilon to order epsilon15 and focused to subwavelength waist radius, are shown to accelerate protons and bare nuclei to several hundred MeV per nucleon over a distance equivalent to a few laser wavelengths.

Fields of a radially polarized laser beam developed recently [Y. I. Salamin, Opt. Lett.31, 2619 (2006)] are employed to show that electrons produced by atomic ionization near the focus may be accelerated to GeV energies. Conditions for producing a mono-energetic and well-collimated electron beam are discussed.

Analytic expressions for the fields of a tightly focused Gaussian laser beam are derived, accurate to ε11, where ε is the diffraction angle. It is found that, for example, using the derived fields, the calculated power can be about
25% more accurate than when calculated using the paraxial approximation for a beam focused down to a waist radius w0∼0...

Analytic expressions for the fields of a tightly focused radially polarized Gaussian laser beam are derived, accurate to epsilon5, where epsilon is the associated diffraction angle. The fields satisfy Maxwell's equations, and the calculated beam power based on them is significantly different from that of the paraxial-approximation fields.

Explicit truncated series expressions modelling the fields of a focused radially polarized Gaussian laser beam are derived, accurate to order ε15, where ε is the associated fundamental Gaussian beam diffraction angle. The new terms make significant corrections to the known paraxial field components, the corrected fields satisfy Maxwell's equations...

We present a simple analytic expression for the generalized diagonal matrix element for arbitrary β and fixed l, using the fully relativistic hydrogen wavefunctions. On the basis of this expression, exact matrix elements corresponding to the value of l in the range n - 5 ≤ l ≤ n - 1 are obtained and shown to reduce to their nonrelativistic counterp...

We employ the lowest-order radially polarized axicon fields of a
Gaussian laser beam to demonstrate that electrons may be accelerated
from rest in vacuum to a few GeV. Petawatt power laser beams focused
onto micron-size focal spots result in multi-TeV/m electron energy
gradients.

Recent advances in laser technology have pushed the frontier of maximum intensity achieved to about 1022W/cm2 and investigators currently believe even higher intensities may be reached in the near future. This, combined with other breakthroughs on the
fronts of short pulse generation and high repetition rates, have stimulated considerable progress,...

The dynamics of electrons injected sideways into the focal region of a tightly-focused laser beam of present-day intensity is studied by numerically solving the relativistic energy–momentum transfer equations. Correlations such as and θ–ζ are investigated, where is the ejection energy, ζ is the injection angle, and θ is the ejection angle (both mea...

The fields of two linearly-polarized, co-propagated laser beams differing slightly in frequency are modelled by those of a tightly focused Gaussian beam. When a single electron is injected sideways into or near the common focus of the two beams, it gets captured and violently accelerated, reaching a maximum energy gain in excess of 2 GeV from beams...

Quantum signatures of a free electron in interaction with a continuous-wave radiation field are investigated by looking for negativities in the Wigner function of the system. The free-electron wave function in the radiation field is calculated fully analytically by solving the appropriate Schrödinger equation in the Krammers-Henneberger frame. It i...

Results from numerical calculations of the energy gain, by a single electron injected sideways into the focal point of a tightly focused laser beat wave, are presented and discussed. Maximum gain, of a few GeV is demonstrated, from the beat structure of two beams of present-day intensity. All results are obtained from solving the relativistic equat...

We investigate optimum conditions for achieving maximum energy gain when electrons are scattered by tightly focused laser beams. A single-beam configuration and one that employs two beams crossing at an angle are discussed. Solution of the equations of motion is carried out numerically in each case, and the fields are modeled by those of a Gaussian...

Electron motion and harmonic generation are investigated in the crossed-beam laser-accelerator scheme in a vacuum. Exact solutions of the equations of motion of the electron in plane-wave fields are given, subject to a restricted set of initial conditions. The trajectory solutions corresponding to axial injection are used to calculate precise emiss...

An electron injected sideways into the focal region of a tightly-focused laser beam encounters strong field variations in both space and time. Thus, momentum may be imparted to it by the field in the nature of a small number of violent impulses. Results from single-particle calculations are presented which demonstrate electron acceleration to GeV e...

By numerically solving the relativistic equations of motion of a single electron in laser fields modeled by those of a Gaussian beam, we demonstrate electron capture by, reflection from, and transmission through the beam. In modeling the fields, terms of order up to ϵ5, where ϵ is the diffraction angle, are retained. All cases of capture are accomp...

By numerically solving the relativistic equations of motion of a single
electron in laser fields modeled by those of a Gaussian beam, we
demonstrate electron capture by, reflection from, and transmission
through the beam. In modeling the fields, terms of order up to
ɛ5, where ɛ is the diffraction angle, are
retained. All cases of capture are accomp...

State-of-the-art petawatt laser beams may be focused down to few-micron spot sizes and can produce violent electron acceleration as a result of the extremely intense and asymmetric fields. Classical fifth-order calculations in the diffraction angle show that electrons, injected sideways into the tightly focused laser beam, get captured and gain ene...

The relativistic dynamics of single particles and thin crystals is
investigated in very short, intense laser pulses. Single particle
acceleration from 100 MeV to GeV energies is shown for electrons in
Gaussian beams of few micron widths and crossed laser beams of 0.1
radians crossing angles. High harmonic generation in the X-ray regime is
predicted...

We solve exactly analytically the relativistic equation of motion of a single electron injected initially at an angle to the direction of propagation of a circularly-polarized plane-wave laser field, of arbitrary intensity, and a uniform electric field. It is shown, in principle, that the electron may be accelerated to high energies in this environ...

An exact analytical solution for the equation of motion of a single relativistic electron, injected initially at some angle ξ to the propagation direction of a linearly polarized plane-wave laser field of arbitrary intensity and a uniform electric field oriented anti-parallel to the laser propagation direction, is developed. The solution is then us...

In general, theoretical analysis of the interaction of a single electron with the radiation field, in vacuum, may be carried out at various levels of sophistication, with the transition from one level to the next made on clear physical grounds. Under conditions to be described below, a nonrelativistic classical description is adequate. However, in...

We present an exact analytic investigation of the electron dynamics in the field of two linearly polarized interfering copropagating laser beams of different frequencies, arbitrary intensities, and arbitrary relative polarizations. In one part of the paper, the laser fields are modelled by plane waves and in another part the fields are allowed to h...

We study the relativistic dynamics of a single electron in a plane-wave laser field and a static magnetic field oriented along the laser propagation direction. A set of exact solutions, that demonstrate acceleration to TeV energies in vacuum by the mechanism of resonance between the electron cyclotron frequency and the Doppler-shifted laser frequen...