Gerard Mourou

Bio: Gerard Mourou is an academic researcher from École Polytechnique. The author has contributed to research in topics: Laser & Ultrashort pulse. The author has an hindex of 82, co-authored 653 publications receiving 34147 citations. Previous affiliations of Gerard Mourou include University of Michigan & San Diego State University.

Generation of microjoule 65-fsec pulses at high-repetition rate

Abstract: Many significant advances have been made recently in the generation and amplifiction of ultrashort optical pulses. Control of the oscillator dispersion and phase modulation has proven useful in improving the pulse width and pulse stability of ultrashort pulse dye lasers.1 The additional bandwidth provided by self-phase modulation (SPM) in optical fibers has enabled the generation of ultrashort pulses by pulse compression.2 Finally, new amplifier systems have been developed which allow the amplification of femtosecond pulses to the microjoule level at kilohertz repetition rates.3,4 In this paper we report the generation of 65-fsec microjoule pulses at a high repetition rate using an actively mode-locked Nd:YAF-based system.

Waveguides : Experiment and Simulation

Abstract: Abstruct-ExperimentaI results are presented for subpicosecond pulse propagation on normal-metal, coplanartransmission-line structures. The pulse distortion that occurs is modelled using a semiempirical curve fit to the fullwave analysis for the modal dispersion and quasi-static approximations for the conductor and radiation loss. Without using any adjustable parameters, very good agreement is obtained for the delay, rise time and amplitude of the pulse for various propagation distances. For terahertz-bandwidth pulses on lines similar to the one studied, the modal dispersion and radiation losses are the dominant pulse-shaping mechanisms. ICOSECOND pulses propagating on normal-metal, P coplanar-circuit interconnects are degraded by the dispersion and attenuation characteristics of these guided-wave structures [ 13 - [3]. The dispersion of a coplanar transmission line arises primarily due to the dielectric inhomogeneity at the surface [4] and the complex surface impedance of the electrodes. The attenuation is due to the conductor losses, substrate conductivity losses and radiation or surface wave losses [5]. Modeling of picosecond pulse propagation on coplanar lines needs to incorporate the previous effects, while trying to retain simplicity in computation through the use of approximations verified via simulations and experiments. In this letter, we present experimental results on subpicosecond pulse propagation on normal-metal coplanar-waveguide (CPW) transmission lines defined on a semi-insulating GaAs substrate. We have considerably extended the bandwidth as compared to previously published results [ 13 - [3], and data for various propagated distances are presented. Simulation is done using a semiempirical curve fit to the fullwave analysis for modal dispersion [4], and quasi-static approximation for the conductor [l] and radiation loss [6]. Excellent agreement is obtained for the important pulse parameters-propagation delay, rise time and pulse amplitude -without the use of any adjustable parameters. For the typical dimensions of the coplanar lines and the frequency bandwidth of the pulse considered here, the distortion of the pulse shape is dominated by the modal dispersion (caused by the dielectric mismatch at the surface), and the loss is domi

Nonlinear Optics in the Relativistic Regime

Abstract: Novel nonlinear optical effects, such as wake-field generation and relativistic self-focusing, are observed when a terawatt laser is focused to an intensity approaching 1019 W/cm2 into a gas jet.

Ion acceleration with few-cycle relativistic laser pulses from foil targets

Abstract: Ion acceleration resulting from the interaction of 11 fs laser pulses of ∼ 35 mJ energy with ultrahigh contrast (<10−10) and 1019 W cm−2 peak intensity with foil targets made of various materials and thicknesses at normal (0°) and 45° laser incidence is investigated. The maximum energy of the protons reached ∼1.4 MeV accelerated in the laser propagation direction and ∼1.2 MeV in the opposite direction from a formvar target. The energy conversion efficiency from the laser to the proton beam is estimated to be as high as ∼1.4% at 45° laser incidence using a 51 nm thick Al target. The high laser contrast indicates the predominance of vacuum heating via Brunel’s effect as an absorption mechanism involving a tiny pre-plasma at the target front. The experimental results are in reasonable agreement with theoretical estimates, where proton acceleration from the target front side in the backward direction is well explained by the Coulomb explosion of a charged cavity formed in a tiny pre-plasma, while forward proton acceleration is likely to be a two-step process: protons are first accelerated in the target front-side cavity and then further boosted in energy through the target back side via the target normal sheath acceleration (TNSA) mechanism.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Phd by thesis

Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

A roadmap for graphene

Abstract: Recent years have witnessed many breakthroughs in research on graphene (the first two-dimensional atomic crystal) as well as a significant advance in the mass production of this material. This one-atom-thick fabric of carbon uniquely combines extreme mechanical strength, exceptionally high electronic and thermal conductivities, impermeability to gases, as well as many other supreme properties, all of which make it highly attractive for numerous applications. Here we review recent progress in graphene research and in the development of production methods, and critically analyse the feasibility of various graphene applications.

Black Hole Explosions

Abstract: QUANTUM gravitational effects are usually ignored in calculations of the formation and evolution of black holes. The justification for this is that the radius of curvature of space-time outside the event horizon is very large compared to the Planck length (Għ/c3)1/2 ≈ 10−33 cm, the length scale on which quantum fluctuations of the metric are expected to be of order unity. This means that the energy density of particles created by the gravitational field is small compared to the space-time curvature. Even though quantum effects may be small locally, they may still, however, add up to produce a significant effect over the lifetime of the Universe ≈ 1017 s which is very long compared to the Planck time ≈ 10−43 s. The purpose of this letter is to show that this indeed may be the case: it seems that any black hole will create and emit particles such as neutrinos or photons at just the rate that one would expect if the black hole was a body with a temperature of (κ/2π) (ħ/2k) ≈ 10−6 (M/M)K where κ is the surface gravity of the black hole1. As a black hole emits this thermal radiation one would expect it to lose mass. This in turn would increase the surface gravity and so increase the rate of emission. The black hole would therefore have a finite life of the order of 1071 (M/M)−3 s. For a black hole of solar mass this is much longer than the age of the Universe. There might, however, be much smaller black holes which were formed by fluctuations in the early Universe2. Any such black hole of mass less than 1015 g would have evaporated by now. Near the end of its life the rate of emission would be very high and about 1030 erg would be released in the last 0.1 s. This is a fairly small explosion by astronomical standards but it is equivalent to about 1 million 1 Mton hydrogen bombs. It is often said that nothing can escape from a black hole. But in 1974, Stephen Hawking realized that, owing to quantum effects, black holes should emit particles with a thermal distribution of energies — as if the black hole had a temperature inversely proportional to its mass. In addition to putting black-hole thermodynamics on a firmer footing, this discovery led Hawking to postulate 'black hole explosions', as primordial black holes end their lives in an accelerating release of energy.

Materials for terahertz science and technology

Abstract: Terahertz spectroscopy systems use far-infrared radiation to extract molecular spectral information in an otherwise inaccessible portion of the electromagnetic spectrum. Materials research is an essential component of modern terahertz systems: novel, higher-power terahertz sources rely heavily on new materials such as quantum cascade structures. At the same time, terahertz spectroscopy and imaging provide a powerful tool for the characterization of a broad range of materials, including semiconductors and biomolecules.