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The objective of the Apollon 10 PW project is the generation of 10 PW peak power pulses of 15 fs at $1~\text{shot}~\text{min}^{-1}$ . In this paper a brief update on the current status of the Apollon project is presented, followed by a more detailed presentation of our experimental and theoretical investigations of the temporal characteristics of the laser. More specifically the design considerations as well as the technological and physical limitations to achieve the intended pulse duration and contrast are discussed.

Intense lasers of femtosecond pulse duration are known to be drivers for intense electron and ion beams. Those beams, generated at laser intensities exceeding 10 19 W/cm 2 , are known to have unique characteristics and are therefore a subject of intense research world wide. Recently, the parameters of laser driven ion beams have been measured using new methods and it has been demonstrated, that beam patterns on a nanometer scale can be generated and propagated over long distances. We report on recent results and prospects for future application with special respect to further laser developments.

We present a technique for simultaneous focusing and energy selection of high-current, mega–electron volt proton beams with the use of radial, transient electric fields (10 7 to 10 10 volts per meter) triggered on the inner walls of a hollow microcylinder by an intense subpicosecond laser pulse. Because of the transient nature of the focusing fields, the proposed method allows selection of a desired range out of the spectrum of the polyenergetic proton beam. This technique addresses current drawbacks of laser-accelerated proton beams, such as their broad spectrum and divergence at the source.

This paper reports the results of a series of experiments on laser generated ions using the 100 TW laser at the ‘Laboratiore pour l’Utilisation des Lasers Intenses (LULI)’ at the Ecole Polythechnique in Palaiseau, France, and the 30 TW ‘Trident’ facility at Los Alamos National Laboratories in New Mexico, USA. It shows the importance of the ‘Target Normal Sheath Acceleration’ process (TNSA) for short pulse laser generated ion beams and its connection to the influence of target properties on the ion beam quality. It is shown that TNSA-generated protons form an ion beam with superior beam quality, following versatile spatial beam shaping approaches. These insights are set into perspective for a fast ignitor scenario based on short pulse laser generated protons.

Recent experimental results on ion beams produced in high-intensity laser–solid interactions indicate the presence of very intense electric fields in the target. This suggests the possibility of efficiently heating a solid material by means of the fast electrons created during the laser–solid interactions and trapped in the target, rather than by the laser photons themselves. We tested this mechanism by irradiating very small cubic aluminum targets with the LULI 100-TW, 300-fs laser at 1.06-μm wavelength. X-ray spectra were measured with an ultra-fast streak camera, coupled to a conical Bragg crystal, providing spectra in the 1.5-keV range with high temporal and spectral resolution. The results indicate the creation of a hot plasma, but a very low coupling between the rapid electrons and the solid. A tentative explanation, in agreement with other experimental results and with preliminary particle-in-cell (PIC) simulations, points out the fatal role of the laser prepulse.

We present a high-contrast 10-fs Front-End for Ti:sapphire PW-lasers within the Apollon-10PW project. This injector uses OPCPA pumped at 100Hz by Yb-based CPA chain. Combination of OPCPA and XPW permits a >1012 contrast ratio.

International audience; Applications using multi-PW lasers necessitate high temporal pulse quality with a tremendous contrast ratio (CR). The first crucial prerequisite to achieve multi-PW peak power is the generation of ultrashort pulses with good spectral phase quality. Second, to avoid any deleterious pre-ionization effect on targets, nanosecond contrast better than 10$^{12}$ is also targeted. In the framework of the Apollon 10 PW French laser program, we present a high-contrast 10 fs front-end design study to inject highly energetic Ti:sapphire PW lasers. The CR has been measured and analyzed in different time ranges highlighting the different major contributions for each scale.

Monomode guiding over 100 Rayleigh lengths (10 cm) of high intensity ultrashort laser pulses ( ${10}^{16}\mathrm{W}/{\mathrm{cm}}^{2}$, 120 fs) has been demonstrated in hollow dielectric capillary tubes (45--70 \ensuremath{\mu}m internal diameter) without inner wall damage. Analytical predictions for coupling conditions and damping length are confirmed experimentally for tubes under vacuum. With 5 to 40 mbar of He gas in the tube, when laser ionization occurs the energy and duration of the transmitted pulse decrease while its spectrum is broadened.

A double foil assembly is shown to be effective in tailoring the maximum energy produced by a laser-accelerated proton beam. The measurements compare favorably with adiabatic expansion simulations, and particle-in-cell simulations. The arrangement proposed here offers for some applications a simple and passive way to utilize simultaneously highest irradiance lasers that have best laser-to-ion conversion efficiency while avoiding the production of undesired high-energy ions.

Soft x-ray spectra (10-70 ˚ A) from carbon and aluminium plasmas produced by high- intensity laser pulses have been studied as a function of laser pulse duration (130 fs-1.3 ps) and intensity (10 14 -5 10 17 Wc m 2 ) for two different laser wavelengths (248 and 800 nm). The x-ray energy emitted from the plasma into specific lines and into the continuum has been measured by means of an absolutely calibrated x-ray spectrograph and thus allows the water window x-ray yield from plasmas produced by long and short wavelength laser radiation to be compared directly. Comparison was made between the dependence of the x-ray energy and width of the x-ray lines on the laser pulse duration, wavelength and intensity. The experimental results have been related to hydrocode simulations.

A diagnostic currently being used for ultrashort pulse laser matter interactions at the Lawrence Livemore National Laboratory is presented. Two cylindrical curved crystals are used as collection optics and diffractive elements in the von Hamos geometry. The dispersed x rays are focused onto the slit of an ultrafast x-ray streak camera. The small nature of the streak camera allows the diagnostic to be positioned close to the target, maximizing the solid angle. Using the geometric layout, the spectral resolution is estimated at E/ΔE∼1000.

Retrieving the characteristics of hot electrons produced in the interaction between solid targets and ultra-intense (I?>?1018?W?cm?2) laser pulses is essential for achieving?progress in our understanding of the interaction physics, which is?key for optimizing numerous downstream applications. Until now, various methods have been used, direct or indirect, but no correlation and no assessment of their respective merits were performed. Here we compare results retrieved from four different diagnostics, direct or indirect, as well as local or non-local, i.e. spectrometry of electrons, spectrometry of the protons accelerated by the electrons and optical probing of these beams expanding into vacuum from the targets. We show that measurements obtained locally at the target rear surface are consistent with those far away from the target and that one can use the diagnostics of the co-moving proton beams to retrieve information about electrons.

High-harmonic generation (HHG) from solid targets driven by ultra-high-intensity lasers is predicted to be a source of attosecond XUV pulses with shorter wavelengths and higher energies than those currently generated in gases [1,2]. A much less explored regime consists in focusing few-cycle pulses down to wavelength-limited spot sizes in order to reach the ultrahigh intensities using mJ pulse energies. This enables HHG from solid targets using waveform-controlled few-cycle pulses readily obtainable from compact kHz laser systems. Here, we show the first experimental demonstration of HHG from solid targets using intense CEP-controlled two-cycle laser pulses.

We demonstrate for the first time kHz-driven high-harmonic generation from solid targets with fully carrier-envelope phase-controlled few-cycle pulses.

International audience; We report the first demonstration of high-harmonic generation from plasma mirrors at a 1 kHz repetition rate. Harmonics up to nineteenth order are generated at peak intensities close to 10$^{18}$ W=cm$^2$ by focusing 1 mJ, 25 fs laser pulses down to 1:7 $\mu$m FWHM spot size without any prior wavefront correction onto a moving target. We minimize target surface motion with respect to the laser focus using online interferometry to ensure reproducible interaction conditions for every shot and record data at 1 kHz with unprecedented statistics. This allows us to unambiguously identify coherent wake emission as the main generation mechanism

We will present the ELI Project consisting in a 200PW laser based high intensity physics users infrastructure. A French single beamline laser prototype called ILE/APOLLON is presently under construction. Associated technological bottlenecks will be described.

We will discuss the two mechanisms involved in high-order harmonic generation from plasma mirrors, and show that they can be clearly identified experimentally. The phase and coherence properties of these harmonics will be analyzed.

We have compared the acceleration of high-energy ions from the rear surface of thin foils for various prepulse contrast conditions of the ultraintense laser pulse irradiating the targets. The experiments were performed using the Laboratoire pour I'Utilisation des Lasers Intenses 100-TW laser facility with 15-20 J energy pulses of >1018 W/cm2 intensity irradiating aluminum targets of variable thicknesses. The laser pulse contrast ratio ahead of the main pulse (prepulse) was varied using either a fast Pockels cell or a single or double plasma mirror (PM). The latter was installed at an intermediate field position, in between the focusing optics and the target. This way, the effect of reducing the laser prepulse by the PM was optimized. With both methods improving the laser pulse contrast, we have observed that one can significantly reduce the thickness of the target used for proton acceleration and, at the same time, increase 1) the maximum energy of the accelerated protons and 2) the energy conversion efficiency of the process. This offers interesting perspectives from high-energy (5-10 MeV) ion acceleration using sub-petawatt laser facilities. A full characterization of contrast enhancement due to the PM, as well as a detailed analysis of the accelerated proton beams, is presented.

The post‐acceleration of laser‐generated protons through conventional drift tube linear accelerators has been simulated with the particle code Parmela. The proton source is generated on the rear surface of a target irradiated by an high‐intensity (1019 W⋅cm−2) short‐pulse (350 fs) laser and focused by a microlens that allows selecting collimated protons at 7±0.1 MeV with rms unnormalized emittance of 0.180 mm.mrad. The simulations show that protons can be accelerated by one drift tube linac tank to more than 14 MeV with unnormalized emittance growth of 8 in x and 22.6 in y directions when considering a total proton charge of 0.112 mA. This result shows for the first time that coupling between laser‐plasma accelerators with traditional accelerators is possible, allowing a luminosity gain for the final beam.

High-energy petawatt lasers require large diffraction gratings for pulse compression. As an alternative to meter-sized gratings, we demonstrate the capability of a tiled-grating system to compress multiterawatt subpicosecond laser pulses. Using a 100 TW-class Nd:glass chirped-pulse amplification laser facility, we report on the performance of a two-grating mosaic to compress high-energy pulses to 2.5 J, 450 fs (5.5 TW) in air with a beam size of 50 mm and energy transmission of 63%. Stability of the grating mosaic alignment was realized by use of an accurate nanopositioning optomechanical system. The output Gaussian spectrum was preserved from grating-gap spectral clipping and was free of modulation.

Specular reflection is one of the most fundamental processes of optics. At moderate light intensities generated by conventional light sources this process is well understood. But at those capable of being produced by modern ultrahigh-intensity lasers, many new and potentially useful phenomena arise. When a pulse from such a laser hits an optically polished surface, it generates a dense plasma that itself acts as a mirror, known as a plasma mirror (PM). PMs do not just reflect the remainder of the incident beam, but can act as active optical elements. Using a set of three consecutive PMs in different regimes, we significantly improve the temporal contrast of femtosecond pulses, and demonstrate that high-order harmonics of the laser frequency can be generated through two distinct mechanisms. A better understanding of these processes should aid the development of laser-driven attosecond sources for use in fields from materials science to molecular biology.

We present and characterize a very efficient optical device that employs the plasma mirror technique to increase the contrast of high-power laser systems. Contrast improvements higher than 10(4) with 50% transmission are shown to be routinely achieved on a typical 10 TW laser system when the pulse is reflected on two consecutive plasma mirrors. Used at the end of the laser system, this double plasma mirror preserves the spatial profile of the initial beam, is unaffected by shot-to-shot fluctuations, and is suitable for most high peak power laser systems. We use the generation of high-order harmonics as an effective test for the contrast improvement produced by the double plasma mirrors.

The acceleration of high-energy ion beams (up to several tens of MeV per nucleon) following the interaction of short ( t < 1ps ) and intense (Iλ2 > 1018W cm-2μm2) laser pulses with solid targets has been one of the most active areas of research in the last few years. The exceptional properties of these beams (high brightness and high spectral cutoff, high directionality and laminarity, short burst duration) distinguish them from those of the lower energy ions accelerated in earlier experiments at moderate laser intensities. In view of these properties, laser-driven ion beams can be employed in a number of groundbreaking applications in the scientific, technological and medical areas. This paper reviews the current state-of-the-art, highlights recent developments and indicate future directions of this research area.

High harmonic generation from ultra-intense laser-matter interaction can be generated by both linear and relativistic means. In experiments with intensity up to a few 10 19 Wcm -2 , we show the distinctions and means to control each.

Laser‐accelerated ion sources open new opportunities for ion beam generation and control, and could stimulate development of compact ion accelerators for many applications. The mechanisms of proton acceleration with solid targets have been intensively studied over the past years, and new target or laser setups are now needed to obtain even higher maximum proton energies. PIC simulations have shown that using ultra thin targets, the maximum proton energy can be greatly increased. The laser can pass through the target and heat target electrons more efficiently. Experiments were conducted to test the feasibility of ultra thin targets laser interaction. PIC simulations were performed and successfully compared to the experimental results. Recently, experiments have shown that a gaseous target can produce proton beams with characteristics comparable to those obtained with solid targets. PIC simulations were also used to study proton acceleration with an underdense target. The optimum thickness obtained corresponds to the thickness where the laser absorption and transmission are equal, and depends greatly on laser and target parameters. The plasma hot electron temperature has also been found to depend on both laser and target parameters. We developed a simple model for the scaling of the optimum thickness for proton acceleration on target and laser parameters.

The extension of time-resolved X-ray diffraction to the subpicosecond domain is an important challenge, as the nature of chemical reactions and phase transitions is determined by atomic motions on these timescales. An ultimate goal is to study the structure of transient states with a time resolution shorter than the typical period of vibration along a reaction coordinate (around 100 fs). Biological processes that can be initiated optically have been studied extensively by ultrafast infrared, visible and ultraviolet spectroscopy1. But these techniques probe only electronic states, whereas time-resolved crystallography should be able to directly monitor atomic positions. Here we show that changes in the X-ray diffraction pattern from an organic film heated by a laser pulse can be monitored on a timescale of less than a picosecond. We have studied the response of a Langmuir–Blodgett multilayer film of cadmium arachidate to laser heating by observing changes in the intensity of one Bragg peak for different delays between the perturbing optical pulse and the X-ray probe pulse. A strong decrease in intensity is seen within a picosecond of heating, resulting from disorder introduced to the layers of cadmium atoms before thermal expansion of the film (which ultimately leads to its destruction) has time to occur.

Since their discovery, laser accelerated ion beams have been the subject of great interest. The ion beam peak power and beam emittance is unmatched by any conventionally accelerated ion beam. Due to the unique quality, a wealth of applications has been proposed, and the first experiments confirmed their prospects. Laser ion acceleration is strongly linked to the generation and transport of hot electrons by the interaction of ultra-intense laser light with matter. Comparing ion acceleration experiments at laser systems with different beam parameters and using targets of varying thickness, material and temperature, some insight on the underlying physics can be obtained. The paper will present experimental results obtained at different laser systems, first beam quality measurement on laser accelerated heavy ions, and ion beam source size measurements at different laser parameters. Using structured targets, we compare information obtained from micro patterned ion beams about the accelerating electron sheath, and the influence of magnetic fields on the electron transport inside conducting targets.

The comparative efficiency and beam characteristics of high-energy ions generated by high-intensity short-pulse lasers (approximately 1-6 x 10(19) W/cm2) from both the front and rear surfaces of thin metal foils have been measured under identical conditions. Using direct beam measurements and nuclear activation techniques, we find that rear-surface acceleration produces higher energy particles with smaller divergence and a higher efficiency than front-surface acceleration. Our observations are well reproduced by realistic particle-in-cell simulations, and we predict optimal criteria for future applications.

We investigate the harmonics generation from a pure dielectric target when submitted to laser intensities in the 1O'8W/crn2. We demonstrate the negative influence of the prepulses and ASE by addressing the direct comparison of the harmonic spectra with and without the introduction of a perfectly controlled plasma mirrorsystem. Harmonics up to the 20th of the fundamental of the Ti-Sa laser are clearly visible in a situation free ofany plasma expansion. 1. INTRODUCTION It is now well known that, due to the non linear electronic response, the focalization of an intense laser pulse on anatomic vapour gives rises to an harmonics spectra consisting in narrow peaks separated by twice the frequencyof the laser driving field. For symmetry reasons, only odd harmonics can be produced. Such high harmonicgeneration makes avaible brilliant XUV sources, with pulse duration in the sub-picosecond regime. The emissionprocess is now well understood : under the laser field, an electron may be ejected into the atom continuum andreturn back to its initial ion when the electric field reverse its direction. It has then the possibility to recombine

We demonstrate the use of a plasma mirror to obtain 60-fs 10-TW laser pulses with a temporal contrast of 10(8) on a nanosecond time scale and 10(6) on a picosecond time scale, and we use these high-contrast pulses to generate high harmonics by nonlinear reflection on a plasma with a steep electronic density gradient. Well-collimated harmonics up to 20th order are observed for a laser intensity of approximately equal to 3 x 10(17) W/cm2, whereas no harmonics are obtained without the plasma mirror.

An ultra fast, sub-picosecond resolution streak camera has been recently developed at the LLNL. The camera is a versatile instrument with a wide operating wavelength range. The temporal resolution of up to 300 fs can be achieved, with routine operation at 500 fs. The streak camera has been operated in a wide wavelength range from IR to x-rays up to 2 keV. In this paper we briefly review the main design features that result in the unique properties of the streak camera and present its several scientific applications: (1) Streak camera characterization using a Michelson interferometer in visible range, (2) temporally resolved study of a transient x-ray laser at 14.7 nm, which enabled us to vary the x-ray laser pulse duration from ~2-6 ps by changing the pump laser parameters, and (3) an example of a time-resolved spectroscopy experiment with the streak camera.

X-ray spectra of a few picosecond duration were emitted by aluminum, selenium and samarium thin foils irradiated with a 100 TW, 300 fs laser at 0.53 μm wavelength. They were measured in the 1600 eV range with high temporal and spectral resolution, using a high-speed streak camera coupled to a conical Bragg crystal. Gradients were limited by using thin foils (300 to 800 a) deposited on a 50 μm gold pinhole. Frequency Domain Interferometry was set to measure the velocity of the critical density at the rear of the target and deduce the electron temperature. A few picosecond duration X-ray spectra have been measured. Sm spectra showed no spectral features in the measured wavelength range, providing a spectrally homogeneous backlighter for absorption spectroscopy. The duration of the emission was shorter when observed through a pinhole. 1-D hydrodynamic simulations coupled to an atomic collisional-radiative code have been used to simulate the X-ray emission of aluminum. The main features of the experimental time resolved spectra, obtained for the pinhole target have been well reproduced, for an initial temperature of 700 ± 100 eV.

The construction of short-pulse tunable soft x-ray free electron laser sources based on the self-amplified spontaneous emission process will provide a major advance in capability for dense plasma-related and warm dense matter (WDM) research. The sources will provide 1013 photons in a 200-fs duration pulse that is tunable from approximately 6 to 100 nm. Here we discuss only two of the many applications made possible for WDM that has been severely hampered by the fact that laser-based methods have been unavailable because visible light will not propagate at electron densities of ne ≥ 1022cm-3. The next-generation light sources will remove these restrictions. © 2003 Optical Society of America.

The Stanford Linear Accelerator Center, in collaboration with Argonne National Laboratory, Brookhaven National Laboratory, Los Alamos National Laboratory, Lawrence Livermore National Laboratory, and the University of California at Los Angeles, have collaborated to create a conceptual design for a Free-Electron-Laser (FEL) R&D facility operating in the wavelength range 1.5-15 {angstrom}. This FEL, called the ''Linac Coherent Light Source'' (LCLS), utilizes the SLAC linac and produces sub-picosecond pulses of short wavelength x-rays with very high peak brightness and full transverse coherence. The first two-thirds of the SLAC linac are used for injection into the PEP-II storage rings. The last one-third will be converted to a source of electrons for the LCLS. The electrons will be transported to the SLAC Final Focus Test Beam (FFTB) Facility, which will be extended to house a 122-m undulator system. In passing through the undulators, the electrons will be bunched by the force of their own synchrotron radiation to produce an intense, spatially coherent beam of x-rays, tunable in energy from 0.8 keV to 8 keV. The LCLS will include two experiment halls as well as x-ray optics and infrastructure necessary to make use of this x-ray beam for research in a variety of disciplines suchmore » as atomic physics, materials science, plasma physics and biosciences. This Conceptual Design Report, the authors believe, confirms the feasibility of constructing an x-ray FEL based on the SLAC linac.« less

The construction of short pulse (10 greater than third generation sources. Further, the high intensity upgrade of the GSI accelerator facilities will lead to specific energy depositions up to 200 kJ/g and temperatures between 1 and 10 eV at almost solid-state densities, enabling interesting experiments in the regime of nonideal plasmas, such as the evolution of intense ion beams in the interior of a Jovian planet. Below we discuss several applications: the creation of warm dense matter (WDM) research, probing of near solid density plasmas, and laser–plasma spectroscopy of ions in plasmas. The study of dense plasmas has been severely hampered by the fact that laser-based methods have been unavailable and these new fourth generation sources will remove these restrictions.

We present the results of a detailed study on the acceleration of intense ion beams by relativistic laser plasmas. The experiments were performed at the 100 TW laser at the Laboratoire pour L'Utilisation des Lasers Intenses. We investigated the dependence of the ion beams on the target conditions based on theoretical predictions by the target normal sheath acceleration mechanism. A strong dependence of the ion beam parameters on the conditions on the target rear surface was found. We succeeded in shaping the ion beam by the appropriate tailoring of the target geometry and we performed a characterization of the ion beam quality. The production of a heavy ion beam could be achieved by suppressing the amount of protons at the target surfaces. Finally, we demonstrated the use of short pulse laser driven ion beams for radiography of thick samples with high resolution.

Ultra-short x-ray sources are generated by focusing sub- picosecond lasers on massive targets. The emission duration of a samarium x-ray source produced with a 100 TW sub- picosecond laser was measured using an ultra-fast X-ray streak camera. The spectral range was limited around 7.5-8.5 angstrom, the range in which samarium can be used as a backlighter for K(alpha) aluminum absorption experiments. The spectral time-evolution and the duration of samarium emission were measured. Preliminary calculations performed with non-local-thermodynamic equilibrium atomic physics show the plasma cooling which occurs with a characteristic time longer than predicted by radiative hydrocode simulations.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The emission from plasmas created with fs-lasers provides sub-picosecond x-ray pulses in the keV-range. Intense emission of K(alpha) lines as well as quasi continuum x-rays can be used for time-resolved diffraction and spectroscopy, i.e. to study lattice or atomic dynamics with sub-picosecond resolution by using a laser pump x-ray probe technique. The x-ray yield and x-ray pulse duration of the laser plasma source depend on the laser parameters and the target design, such as intensity, laser wavelength, pulse duration and prepulse level. To accumulate as many photons as possible of the isotropic source an efficient large aperture optic has to be used to select an x-ray line or a wavelength range and focus the radiation onto the sample. It is shown that the use of toroidally bent crystals provides the possibility to refocus 10-4 of the photons emitted in the whole solid angel to spot size of around 80 micrometers with a temporal broadening below 100 fs. Combinations of bent focusing crystals with a flat sample crystal for fast x-ray diffraction application are discussed. Experiments showing the temporal response of laser heated crystals are presented and compared with theoretical simulations based on Takagi-Taupin theory.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

High resolution infrared imaging system calls for very long scanning arrays with several thousands of detectors and high performance. This paper presents the technological developments and the electro-optical performance obtained at LETI/SLIR (Infrared Laboratory) on linear HgCdTe (MCT) arrays working in the 3-5, 8-10 and 11-12.5 micrometers spectral ranges. These large arrays have an indirect hybrid architecture composed of butted HgCdTe PV detection circuits and Si readouts hybridized on a mechanically close-matched fanout substrate. Defect free dicing and butting, respecting the detector pitch, is made by accurate and nondamaging techniques.

We have implemented a Ti:sapphire/mixed Nd:glass laser syste at LULI producing sub-picosecond pulses in the 100 TW power range. Focusing to a 1.5-times diffraction-limited spot results in a peak intensity on target over 10 19 W/cm 2 . Significant experiments in particle acceleration, X-ray laser and other basic plasma physics researchers have been carried out since this implementation. This paper details the characteristics of the present set-up and the main path of progress towards a high performance petawatt facility.

Optical pump, x-ray diffraction probe experiments have been used to study the lattice dynamics of organic materials using a laser-produced plasma x-ray source. The x-ray source is generated from a 10 Hz, 26 mJ, 120 fs laser beam focused on a silicon wafer target. The emitted K(alpha ) x-ray radiation is used to probe a cadmium arachidate Langmuir-Blodgett film and a TlAP crystal optically perturbed at laser fluences from 1.8 J/cm2 to 27 J/cm2. Ultrafast disordering inside the lattice -- within a time scale below 600 fs to few tens of picoseconds -- is clearly observed and produce a drop of the probe x-ray diffracted signal.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

High resolution infrared imaging system calls for very long scanning arrays with several thousands of detectors and high performance. This paper presents the recent technological developments an the electrooptical performances obtained at LETA/LIR on 1500 detector linear HgCdTe arrays working in the 3-5 and 8-10 micrometers spectral ranges. These very large arrays have an indirect hybrid architecture composed of butted HgCdTe PV detection circuits and Si CMOS readouts hybridized on a fanout substrate. Defect free dicing and butting, respecting the detector pitch, is made by accurate and non damaging techniques.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A 640 X 480 snapshot IRCMOS array with 25 micron pitch operating in the 3 - 5 microns range was fabricated and an image demonstrated at the Infrared Laboratory (LIR). The readout circuit with 2 pC charge handling capacity was designed and processed with a 1.2 micrometer design rules standard CMOS technology. Photovoltaic (PV) detectors were achieved by ion implantation in liquid phase epitaxy MCT layers and interconnected by indium bumps on the readout circuit. A description of the component is given and the main electro-optical characteristics are presented. The pixel operability is greater than 99.8% and a NEDT of 15 mK was measured at half dynamics. Excellent imagery has been obtained with this component operating at 77 K and f/2 optics.

Short-pulse laser-produced plasmas look very promising for the generation of sub-picosecond X-rays. By combining several experimental techniques, we have significantly progressed towards a better understanding of ultrafast laser-matter interaction. The X-ray yield is a sensitive function of the electron density gradient scale length of the target plasma. In this work, the scale length has been changed by varying the temporal separation between the main laser pulse and a lower intensity prepulse. X-ray spectroscopic diagnostics of the plasma parameters have been used from the analysis of resonance and dielectronic satellite lines. The angular and energy distribution of suprathermal electrons emitted during the ultrafast laser- plasma interaction have been measured as a function of laser polarization and prepulse delay. Frequency-domain interferometry and optical measurements of the reflected probe pulse have been used to study the velocity and the gradient scale length of the expanding plasma. The Kα emission yield peaks for a scale length where resonant absorption is optimized. Hydrodynamic simulations have been performed to investigate the plasma dynamics and the basic processes which control the X-ray emission duration and intensity. Applications of ultrashort Kα X-rays to the diagnostic of solid plasma conditions and as a source for time-resolved diffraction and spectroscopy of transient chemical, biological or physical phenomena are underway.

A 256 by 256 IRCMOS array with a 35 micron pitch operating at 88 K and above 10 microns has been developed at LETI/LIR. High performances have been obtained owing on one hand to a reduced dark current detector technology and on the other hand to a new readout circuit architecture which maximizes both charge handling capacity and responsivity. We have measured a NEDT of 13 mK at 88 K for a cutoff wavelength of 10.1 micrometer. A description of the array is given and the main electro-optical characteristics of the component are presented.

High resolution infrared imaging system calls for very long scanning arrays with several thousands of detectors and high performance. This paper presents the recent technological developments carried out at LETI/LIR on long butted arrays and gives the results obtained on a 1500 detector linear HgCdTe array with a 30 micrometer pitch and a 5.5 micrometer cut-off wavelength. This very large array (length approximately equals 50 mm) has an indirect hybrid architecture composed of 5 butted HgCdTe PV detection circuits and 5 Si CMOS readouts hybridized on a mechanically close-matched fanout substrate. Defect free dicing and butting, respecting the detector pitch, is made by accurate and non damaging techniques. A detailed description of the array and the main electro-optical performances are presented.

We present the first measurements of particle velocity histories at the interface between an aluminum sample shocked by a 120 fs laser-driven pressure pulse and a fused silica window. Frequency-domain interferometry is used to provide space- and time-resolved measurements of the phase shift of a pair of probe pulses backscattered at the shocked interface. Pressures of 1--3 Mbar are inferred from the simultaneous measurement of the particle and shock velocities along the aluminum Hugoniot curve for $\ensuremath{\sim}{10}^{14}\mathrm{W}/{\mathrm{cm}}^{2}$ laser irradiances.

We have studied theoretically and experimentally the x-ray production above 1 keV from femtosecond laser plasmas generated on periodically modulated surface targets. Laser energy coupling to plasma surface waves has been modeled using a numerical differential method. Almost total absorption of incident laser radiation is predicted for optimized interaction conditions. Silicon gratings have been irradiated by a 120 fs Ti: sapphire laser at irradiances in excess of 1016W/cm2. X-ray intensities above 1.5 keV (K-shell lines) have been measured as a function of the incidence angle. Results show a distinct x-ray emission maximum for the first order diffraction angle and are in good qualitative agreement with our theoretical predictions.