CEP-stabilized, sub-18 fs, 10 kHz and TW-class 1 kHz dual output Ti:Sa laser with wavelength tunability option.

Generating energetic, few-cycle laser pulses with stabilized carrier-envelope phase at a high-repetition rate constitutes a first step to access the ultra-fast dynamics underlying the interaction of matter with intense, ultrashort pulses in attosecond science or high-field physics. We present here a Ti:Sa-based 1 kHz TW-class laser delivering 17.8 fs pulses with 350 mrad shot-to-shot CEP noise based on an original 10 kHz front-end design. In parallel to this short pulse duration operation mode, it is possible to tune the output wavelength of the front end within a 90 nm range around 800 nm.

Original Ti:Sa 10 kHz front-end design delivering 17 fs, 170 mrad CEP stabilized pulses up to 5 W.

We present a compact 10 kHz Ti:Sa front end relying on an original double-crystal regenerative amplifier design. This new configuration optimizes the thermal heat load management, allowing the production of a 110 nm large spectrum and maintaining a good beam profile quality. The front end delivers up to 5 W after compression, 17 fs pulses with a 170 mrad shot-to-shot residual carrier-envelope phase noise.

Optically controlled solid-density transient plasma gratings.

A general approach for optically controlled spatial structuring of overdense plasmas generated at the surface of initially plain solid targets is presented. We demonstrate it experimentally by creating sinusoidal plasma gratings of adjustable spatial periodicity and depth, and study the interaction of these transient structures with an ultraintense laser pulse to establish their usability at relativistically high intensities. We then show how these gratings can be used as a "spatial ruler" to determine the source size of the high-order harmonic beams produced at the surface of an overdense plasma. These results open new directions both for the metrology of laser-plasma interactions and the emerging field of ultrahigh intensity plasmonics.

Evidence of resonant surface-wave excitation in the relativistic regime through measurements of proton acceleration from grating targets.

The interaction of laser pulses with thin grating targets, having a periodic groove at the irradiated surface, is experimentally investigated. Ultrahigh contrast (~10(12)) pulses allow us to demonstrate an enhanced laser-target coupling for the first time in the relativistic regime of ultrahigh intensity >10(19) W/cm(2). A maximum increase by a factor of 2.5 of the cutoff energy of protons produced by target normal sheath acceleration is observed with respect to plane targets, around the incidence angle expected for the resonant excitation of surface waves. A significant enhancement is also observed for small angles of incidence, out of resonance.

Space- and time-resolved density measurements of a high-intensity laser-produced plasma for x-ray laser studies.

We present a detailed study on the spatiotemporal density evolution of a plasma created by optical-field ionization of a high-pressure pulsed gas jet by a 10-TW, 60-fs Ti:sapphire laser. The plasma dynamics has been studied on a 17-ns time scale with a 60-fs time resolution and a 5-microm space resolution using a Mach-Zehnder interferometer. The density profile and the plasma radial expansion were accurately measured for conditions relevant to x-ray laser schemes in H-like nitrogen which were recently proposed [S. Hulin et al., Phys. Rev. E 61, 5693 (2000)]. The results were reproduced well by hydrocode simulations that allowed to infer the plasma temperature.

Influence of optical thickness and hot electrons on Rydberg spectra of Ne-like and F-like copper ions.

Spectra in the 7.10 to 8.60 A range from highly charged copper ions are observed from three different laser-produced plasmas (LPPs). The LPPs are formed by a 15-ns Nd:glass laser pulse (type I: E(pulse)=1-8 J, lambda=1.064 microm), a 1-ps Nd:glass laser pulse (type II: E(pulse)=1 J, lambda=1.055 microm), and a 60-fs Ti:sapphire laser pulse (type III: E(pulse)=800 mJ, lambda=790 nm). The spectra of high-n (n

Spatially resolved x-ray spectroscopy investigation of femtosecond laser irradiated Ar clusters.

High temperature plasmas have been created by irradiating Ar clusters with high intensity 60-fs laser pulses. Detailed spectroscopic analysis of spatially resolved, high resolution x-ray data near the He(alpha) line of Ar is consistent with a two-temperature collisional-radiative model incorporating the effects of highly energetic electrons. The results of the spectral analysis are compared with a theoretical hydrodynamic model of cluster production, as well as interferometric data. The plasma parameters are notably uniform over one Rayleigh length (600 microm).

Hot-electron influence on L-shell spectra of multicharged Kr ions generated in clusters irradiated by femtosecond laser pulses.

Strong L-shell x-ray emission has been obtained from Kr clusters formed in gas jets and irradiated by 60-500-fs laser pulses. Spectral lines from the F-, Ne- Na-, and Mg-like charge states of Kr have been identified from highly resolved x-ray spectra. Spectral line intensities are used in conjunction with a detailed time-dependent collisional-radiative model to diagnose the electron distribution functions of plasmas formed in various gas jet nozzles with various laser pulse durations. It is shown that L-shell spectra formed by relatively long nanosecond-laser pulses can be well described by a steady-state model without hot electrons when opacity effects are included. In contrast, adequate modeling of L-shell spectra from highly transient and inhomogeneous femtosecond-laser plasmas requires including the influence of hot electrons. It is shown that femtosecond-laser interaction with gas jets from conical nozzles produces plasmas with higher ionization balances than plasmas formed by gas jets from Laval nozzles, in agreement with previous work for femtosecond laser interaction with Ar clusters.

Intense gamma-ray source in the giant-dipole-resonance range driven by 10-TW laser pulses.

A gamma-ray source with an intense component around the giant dipole resonance for photonuclear absorption has been obtained via bremsstrahlung of electron bunches driven by a 10-TW tabletop laser. 3D particle-in-cell simulation proves the achievement of a nonlinear regime leading to efficient acceleration of several sequential electron bunches per each laser pulse. The rate of the gamma-ray yield in the giant dipole resonance region (8

Proton acceleration with high-intensity ultrahigh-contrast laser pulses.

We report on simultaneous measurements of backward- and forward-accelerated protons spectra when an ultrahigh intensity (approximately 5 x 10(18) W/cm(20), ultrahigh contrast (>10(10)) laser pulse interacts with foils of thickness ranging from 0.08 to 105 microm. Under such conditions, free of preplasma originating from ionization of the laser-irradiated surface, we show that the maximum proton energies are proportional to the p component of the laser electric field only and not to the ponderomotive force and that the characteristics of the proton beams originating from both target sides are almost identical. All these points have been corroborated by extensive 1D and 2D particle-in-cell simulations showing a very good agreement with the experimental data.

Probing hot and dense laser-induced plasmas with ultrafast XUV pulses.

In this Letter, we demonstrate the instantaneous creation of a hot solid-density plasma generated by focusing an intense femtosecond, high temporal contrast laser on an ultrathin foil (100 nm) in the 10(18) W/cm2 intensity range. The use of high-order harmonics generated in a gas jet, providing a probe beam of sufficiently short wavelengths to penetrate such a medium, enables the study of the dynamics of this plasma on the 100 fs time scale. The comparison of the transmission of two successive harmonics permits us to determine the electronic density and the temperature with accuracies better than 15%, never achieved up to this date in the regime of laser pulses at relativistic intensity.

Soft-x-ray laser scheme in a plasma created by optical-field-induced ionization of nitrogen

An x-ray laser scheme based on the recombination of a fully stripped nitrogen plasma is presented. Plasma is assumed to be created by the optical-field ionization of a nitrogen gas jet of 10(19) cm-3 atomic density by an ultrashort (60 fs), high-intensity (3 x 10(19) W/cm2) Ti:sapphire laser. Results of two-dimensional particle-in-cell simulations, modeling laser-plasma interaction, parametric heating, and ponderomotive effects are presented. Hydrodynamic and kinetics calculations are performed and predict important local gain for H-like nitrogen transitions at 25 and 134 A, following fast collisional recombination for specific plasma conditions.