Plasma Grating Research Articles

Dynamics of plasma gratings in atomic and molecular gases

The decay of the plasma grating formed at the intersection of two femtosecond filaments is measured in several molecular and atomic gases. The grating evolution is ruled by ambipolar diffusion in atomic gases and by a combination of ambipolar diffusion and collision-assisted free electron recombination in molecular gases. Electron diffusion and recombination coefficients are extracted for Ne, Ar, Kr, Xe, N2, O2, CO2, and air at 1 bar.

Control of third harmonic generation by plasma grating generated by two noncollinear IR femtosecond filaments

A plasma grating is formed by two femtosecond filaments, and the influence of probe filament on the plasma grating is shown. By using the plasma grating, the enhancement of the third harmonic (TH) generated from the probe filament is studied, and more than three orders of magnitude enhancement of TH generation is demonstrated as compared with that obtained from a single filament. The dependences of TH generation on the time delay, the spatial period of plasma grating, the relative polarization and the crossing position between the probe beam and the two pump beams are investigated. The spectral broadening of TH generated from the probe filament induced by the interaction between the probe filament and the plasma grating is also studied.

Supercontinuum enhancement and transfer induced by a plasma grating in air

We experimentally investigate the plasma grating created by two intersecting ultrashort laser pulses, and its effects on the supercontinuum generated from femtosecond laser filamentation. The enhanced supercontinuum generation is observed, with a plasma grating formed. And an energy transfer of the supercontinuum is demonstrated, from one pulse to the other, due to the diffraction property of plasma grating. The theoretical calculation accords well with the experimental result.

Two-dimensional plasma grating by non-collinear femtosecond filament interaction in air

We experimentally demonstrated that two-dimensional (2D) plasma gratings could be generated in air by nonlinear interaction of three femtosecond filaments. The intensity interference of non-collinearly overlapped filaments was self-projected along a relatively long distance and accompanied with a wavelength-scale periodic change of the refractive index in the encircling air due to periodic plasma density modulation. The 2D plasma gratings supported 2D diffraction of the generated third-harmonic pulses. By using in-line time-resolved holographic imaging and time-delayed diffraction, the 2D plasma gratings were evidenced to last a few tens picoseconds after the excitation pulses.

Effect of a plasma grating on pump–probe experiments near the ionization threshold in gases

Calculations are performed of the phase shift caused by the spatial modulation in the plasma density due to interference between a strong pump pulse and a weak probe pulse. It is suggested that a recent experiment [Opt. Express 17, 13429 (2009)] observed an effective birefringence from this plasma grating rather than from the higher-order Kerr effect.

Generation of High-Density Electrons Based on Plasma Grating Induced Bragg Diffraction in Air

Efficient nonlinear Bragg diffraction was observed as an intense infrared femtosecond pulse was focused on a plasma grating induced by interference between two ultraviolet femtosecond laser pulses in air. The preformed electrons inside the plasma grating were accelerated by subsequent intense infrared laser pulses, inducing further collisional ionization and significantly enhancing the local electron density.

The formation of an intense filament controlled by interference of ultraviolet femtosecond pulses

We experimentally investigated the formation of a wavelength-scale photonic plasma grating induced by interference-assisted coalescence of two noncollinear ultraviolet femtosecond laser pulses. The period of the created plasma grating decreased with the crossing angle of the interacting laser pulses. For a proper small crossing angle, the noncollinear ultraviolet filaments were coalesced and an intense single ultraviolet filament was formed with a diameter of 5 μm which was below the focused limitation. This may provide a way to control ultraviolet femtosecond filamentation.

Intensity clamping during dual-beam interference

One has prospected to overcome the intensity clamping phenomenon during femtosecond laser filamentation by superimposing two beams. This experimental scheme is thus studied in our work. We have realized the interference of two ultrashort laser beams and one of them creates a filament in air. The formation of a dynamic plasma grating induced by the interference pattern is observed. However, qualitative analysis of the experimental results indicates that intensity clamping still governs the intensity evolution during the dual-beam interaction. The expectation of greatly increasing laser intensity by dual beams superposition might not be realistic.

Femtosecond laser pulse energy transfer induced by plasma grating due to filament interaction in air

We experimentally demonstrate the formation of a thin plasma grating lasted for several tens of picosecond induced by the strong interaction between two noncollinear femtosecond filaments in air. A time-delayed second-harmonic pulse propagating along one of the incident filaments is coupled and nonlinearly diffracted by the thin plasma grating, leading to an energy transfer to the other noncollinearly crossed femtosecond filament. The dependences of the plasma grating on the intensity ratios and relative polarizations between the input pulses are investigated.

Energy Exchange between Femtosecond Laser Filaments in Air

We report on the energy exchange between femtosecond laser filaments in air. A traveling plasma grating formed at the intersection of the filaments is proposed to explain the energy transfer. In this moving plasma grating mediated mechanism the laser energy transfers from the lower frequency pulse to its higher frequency partner, while in a traditional Kerr nonlinearity mediated grating, energy transfer occurs in the opposite manner. Based on this mechanism, we demonstrate an energy transfer ratio as high as 50% for pulses with an energy of several millijoules.

The transition from plasma gratings to cavitons in laser-plasma interactions

One-dimensional Vlasov–Maxwell simulations of laser-plasma interactions are presented. It is shown that plasma gratings and density cavitons are formed sequentially. There are strong electromagnetic fields in the cavitons and the electromagnetic structures are nearly standing and long-lived. The formation of gratings and cavitons can be explained by a nonlinear second-order differential equation. The electromagnetic fields trapped in cavitons have both subcycle and cycle structures. Plasma whose density is higher than the critical density can be formed around the cavitons. Gratings and high density plasmas can reflect light in a very high level. This may be detrimental to the inertial confinement fusion.

Femtosecond laser induced plasma diffraction gratings in air as photonic devices for high intensity laser applications

The creation of volume plasma density gratings in air by temporally overlapped high-intensity IR femtosecond laser pulses is demonstrated experimentally. Through the diffraction of various probe beams the plasma grating properties are recovered including its thickness and refractive index modulation, as well as its decay dynamics. The diffraction properties of these plasma photonic devices suggest that they can be used in applications involving high intensity lasers, such as filamentation, where no physical objects can be placed in the path of the laser beams.

Investigation on the dispersion characteristics of a uniform plasma grating

Recently, the plasma Bragg gratings induced by two intersecting laser pulses has been predicted theoretically. The dispersion relation of uniform plasma gratings under the oblique incidence of a light wave is investigated with the transfer-matrix method and the coupled-mode theory. Both approaches show that such plasma gratings exhibit a photonic band gap, near which strong dispersion appears. The photonic band gap has different polarization characteristics when the light wave is obliquely incident on the plasma grating. With the increase of the incident angle, the band gap for an S-polarized wave increases gradually, while that for a P-polarized wave decreases first rapidly, then vanishes when it approaches the Brewster angle, and finally becomes wide with the further increase of the incident angle. Since the plasma grating has an ultrabroad photonic band gap and can support an ultrahigh damage threshold of incident light waves, it has the potential to be a novel photonic device to manipulate extremely intense laser pulses.

Plasma Bragg gratings generated by the interaction of two counter-propagating laser pulses with plasmas

Solutions of electron and ion density gratings at the linear stage are given. Deep plasma gratings produced by the ponderomotive force of the interference of the two intersecting laser pulses are investigated. Dependence of the plasma grating on the plasma density, duration and intensity of the laser pulses are studied with 1D particle-in-cell (PIC) simulation. It is found that the density of peaks of such gratings can be 8 times the initial plasma density and can last a few picoseconds. We have found stable, long-lifetime electromagnetic solitons by use of these gratings. It is shown that the intensity for the formation of relativistic EM solitons with two crossed-propagating pulses is reduced to a great extent.

Degenerate four-wave mixing mediated by ponderomotive-force-driven plasma gratings

Degenerate four-wave mixing mediated by ponderomotive-force-driven plasma gratings is demonstrated in the near-infrared regime. The quadratic dependence of the reflectivity of the probe pulse on plasma density indicates that the mixing is caused by the quasineutral plasma grating driven by the laser ponderomotive force. The experiment verifies that ponderomotive force is an effective means to produce a large-amplitude short-period plasma grating, which has many important applications in ultrahigh-intensity optics. In particular, such a grating is a crucial element for the development of plasma phase-conjugate mirrors that can be used to restore the wave-front distortion that is ubiquitous in nonlinear propagation.

Efficient 20TW Ti:sapphire laser with two stage amplifiers

Propagation of ultrashort intense laser pulses in a plasma Bragg grating induced by two intersecting laser pulses is studied. Such a plasma grating exhibits an ultrawide photonic bandgap, near which the strong dispersion appears. Particle-in-cell (PIC) simulations show the light speed reduction, pulse stretching, chirped pulse compression, and fast compression of Bragg grating solitons in the plasma grating. The nonlinear coupled-mode theory agrees well with the PIC results. Since the plasma grating can support an ultrahigh damage threshold, it can be a novel photonic device to manipulate extremely intense femtosecond laser pulses.

Manipulating intense laser pulses by plasma Bragg gratings

Propagation of ultrashort intense laser pulses in a plasma Bragg grating induced by two intersecting laser pulses is studied. Such a plasma grating exhibits an ultrawide photonic bandgap, near which the strong dispersion appears. Particle-in-cell (PIC) simulations show the light speed reduction, pulse stretching, chirped pulse compression, and fast compression of Bragg grating solitons in the plasma grating. The nonlinear coupled-mode theory agrees well with the PIC results. Since the plasma grating can support an ultrahigh damage threshold, it can be a novel photonic device to manipulate extremely intense femtosecond laser pulses.

Theoretical and experimental results of MMW plasma gratings in silicon quartz image guide technology

The propagation characteristics of an optoelectronically induced plasma grating on a single moded silicon–quartz image guide are experimentally investigated at W-band frequencies and compared with theoretical results based on a transversal homogeneous plasma profile. Because of the long diffusion lengths of the silicon semiconductor considered, an optimum carrier density and, hence, an optimum optical power density is found which results in a maximum magnitude of plasma-induced grating reflection coefficient. To understand the behavior of the reflection coefficient versus charge carrier density, the variation of phase and attenuation constants as a function of carrier density in the dark and excited waveguide sections are investigated. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1928–1932, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21835

Chirped pulse compression in nonuniform plasma Bragg gratings

A nonuniform plasma Bragg grating with a monotonically increasing density-modulation profile can be naturally produced by two Gaussian laser pulses counterpropagating through a homogeneous plasma slab. Such a plasma grating exhibits a nonuniform photonic band gap with a monotonically increasing width. It can be used to compress a positively or negatively chirped pulse. Particle-in-cell simulations show that the compressed pulse has nearly no energy loss and the compression efficiency can exceed 90%.

Manipulating ultrashort intense laser pulses by plasma Bragg gratings

Propagation of ultrashort intense laser pulses in a plasma Bragg grating induced by two intersecting laser pulses is studied. Such a plasma grating exhibits an ultrawide photonic band gap, near which the strong dispersion appears. It is found that the grating dispersion dominates the dispersion of the background plasma by several orders of magnitude. Particle-in-cell (PIC) simulations show the light speed reduction, pulse stretching, chirped-pulse compression, and fast compression of Bragg grating solitons in the plasma grating. The nonlinear coupled-mode theory agrees well with the PIC results. Since the plasma grating can support an ultrahigh damage threshold, it can be a novel photonic device to manipulate extremely intense femtosecond laser pulses.