Electric Field Of Laser Pulse Research Articles

Spatial distribution of the electric field of laser pulses in optical fibers having a gradient profile of the refractive index. Linear case

The aim of the present research is to investigate the spatiotemporal regime of propagation of three-dimensional optical pulses in fibers with spatial dependence of the refractive index. An exact analytical solution of the linearized equation is found. Numerical simulations are conducted of the solutions obtained.

Electron Acceleration by a Radially Polarized Laser Pulse in an Ion Channel

The presence of a preformed ion channel in a laser accelerator enhances the oscillatory velocity of electrons due to the confined motions that leads to increase the energy gain from acceleration. The unique properties of radially polarized laser beam are utilized which leads to improvement in trapping and acceleration of electron so that an electron can be accelerated further to a very high energy level. The enhancement in electron energy is due to fact that the radial field vanishes on axis, but only axial field survives which accelerates the electron longitudinally. The electrostatic field generated by an ion channel stops the electrons to escape from the interaction region due to the transverse oscillations and thus causes a resonance between the electrons and the electric field of laser pulse. Our results show that the combined role of radial polarization and the effect of an ion channel can enhance the electron energy gain significantly.

Conduction band population in graphene in ultrashort strong laser field: Case of massive Dirac particles

The Dirac-like quasiparticles in honeycomb graphene lattice are taken to possess a non-zero effective mass. The charge carriers involve to interact with a femtosecond strong laser pulse. Due to the scattering time of electrons in graphene ([Formula: see text]10–100 fs), the one femtosecond optical pulse is used to establish the coherence effect and, consequently, it can be realized to use the time-dependent Schrödinger equation for electron coupled with strong electromagnetic field. Generalized wave vector of relativistic electrons interacting with electric field of laser pulse causes to obtain a time-dependent electric dipole matrix element. Using the coupled differential equations of a two-state system of graphene, the density of probability of population transition between valence (VB) and conduction bands (CB) of gapped graphene is calculated. In particular, the effect of bandgap energy on dipole matrix elements at the Dirac points and resulting CB population (CBP) is investigated. The irreversible electron dynamics is achieved when the optical pulse end. Increasing the energy gap of graphene results in decreasing the maximum CBP.

Electron acceleration in moving laser-induced gratings produced by chirped femtosecond pulses

We propose nonrelativistic electron acceleration in a vacuum using interaction with two crossed chirped femtosecond laser pulses at different frequencies. Electron energy gain is optimized by the phase-matching of accelerated electron velocity to a maximum of ponderomotive force in the moving intensity grating by linear chirping of both pulses. Particle tracking simulations show acceleration gradients as high as 40 GeV m−1 (energy gain of hundreds of keV) using 25 fs pulses with peak power ≤500 GW. The dependence of electron energy gain and the deflection angle on experimental parameters (the amplitude of the electric field of laser pulses, and the initial phase shift between the electron and intensity grating) was studied in detail.

Photodetachment of negative hydrogen ion in circularly polarized monochromatic and bichromatic laser fields

We theoretically have investigated the detachment of negative hydrogen ion in circularly polarized monochromatic and bichromatic laser fields by calculating the photoelectron momentum distributions (PMDs). We find that the PMDs are controlled by the electric field of laser pulse. For circularly polarized monochromatic laser fields, the PMDs are perfect and isotropic rings, and the photodetachment rates in random direction are same. For this case, the photoelectron momentum spectra directly reflect the electronic distributions of negative hydrogen ion. For circularly polarized bichromatic laser field, the PMDs are inversion asymmetric, but symmetric about a certain axis. The emission directions of the photoelectrons vary with the electric field shape, that is to say that the emission directions of the photoelectrons vary with the carrier-envelope (CE) phases, which decide the electric field of laser pulse. The maximal photodetachment rates and the spectra shape, however, are same for the different CE phases.

Energetic electron propagation in solid targets driven by the intense electric fields of femtosecond laser pulses

An analytical model is used to interpret experimental data on the propagation of energetic electrons perpendicular to and parallel to the propagation direction of intense femtosecond laser pulses that are incident on solid targets. The pulses with ≈1020 W/cm2 intensity are incident normal onto a gadolinium or tungsten wire embedded in an aluminum substrate, and MeV electrons generated in the focal spot propagate along the laser direction into the irradiated wire. Electrons also propagate laterally from the focal spot through the aluminum substrate and into a dysprosium or hafnium spectator wire at a distance up to 1 mm from the irradiated wire. The ratio of the K shell emission from the spectator and irradiated wires is a measure of the numbers and energies of the MeV electrons propagating parallel to and perpendicular to the intense oscillating electric field of the laser pulse. It is found that the angular distribution of electrons from the focal spot is highly non-isotropic, and approximately twice as many electrons are driven by the electric field toward the spectator wire as into the irradiated wire. This quantitative result is consistent with the qualitative experimental observation that the oscillating electric field of an intense femtosecond laser pulse, when interacting with a heavy metal target, preferentially drives energetic electrons in the electric field direction as compared to perpendicular to the field.

THIRD ORDER NONLINEAR EFFECT NEAR A DEGENERATE BAND EDGE

We describe the properties of a 1D anisotropic periodic structure, designed to have a band edge with fourth order degeneracy, called a degenerate band edge (DBE). A giant field resonance at the transmission peak frequency closest to this band edge has been verified by rigorous numerical calculation and is supported by experimental evidence. Simulations are presented of the consequences of a χ3 nonlinear index change at a DBE resonant frequency which can provide all-optical switching and transmission self-limiting.

Sampling without synchronization

An electro–optic scheme for sampling the electric field of laser pulses without the need for any synchronization could become a valuable tool for characterizing sources that emit in the infrared and terahertz regions.

Phase-Controlled Single-Cycle Strong-Field Photoionization

The evolution of the electric field of laser pulses consisting of a few optical cycles depends on the so-called absolute phase. Strong-field photoionization not only provides means to measure the absolute phase. Rather phase-controlled few-cycle pulses allow investigating photoionization on the attosecond time scale as the sub-cycle ionization dynamics becomes manifest in the photoelectron spectra. Few-cycle pulses thus can serve as a time-domain microscope for investigation of electronic transitions.