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.

Demonstration of tailored energy deposition in a laser proton accelerator

Abstract: In order to implement radiotherapy based on a laser accelerator, it is necessary to precisely control the spatial distribution and energy spectrum of the proton beams to meet the requirements of the radiation dose distribution in the three-dimensional biological target. A compact laser plasma accelerator has been built at Peking University, which can reliably generate and transport MeV-energy protons with a specified energy onto the irradiation platform. In this paper, we discuss several technologies for the accurate control of a laser-accelerated proton beam with large divergence angle and broad energy spread, including the determination of the beam source position with micron accuracy, a tuning algorithm for the transport line which we refer to as ``matching-image-point two-dimensional energy analysis'' to realize accurate energy selection, and the control of beam distribution uniformity. In the prototype experiment with low energy protons and 0.5-Hz irradiation rate, a tailored energy deposition is demonstrated, which shows the potential feasibility of future irradiation based on laser-accelerated proton beams.

Superresolved femtosecond laser ablation.

Abstract: The determinist behavior of the femtosecond ablation process allows morphing features well under the diffraction limit by utilizing the thresholding effect, down to the nanometer scale. Because there are a vast range of applications where scaling down the size of the features is a major concern, we investigate the use of superresolving pupil plane filters. As is well known, these filters redistribute the focused optical intensity for a narrower bright spot and, as a trade-off, increase the sidelobes. However, this drawback can be rendered insignificant if all the outer optical power is kept under the determinist threshold value. Two types of pure absorbing binary filter have been tried, giving credence to a size reduction of the ablations in fused silica.

Why ring regenerative amplification (regen)

Abstract: We show that ring cavity regenerative amplifiers (regens) have distinct advantages over the linear ones for applications in chirped pulse amplification. Larger energy, better contrast and better isolation from the oscillator are experimentally demonstrated.

Sweep drive circuit for a streak camera

Abstract: An inexpensive, simple and highly accurate sweep drive circuit for streak cameras generates a ramp voltage for the deflection plates of an image converter tube of a streak camera. A solid state switch is used in a manner which eliminates the need for a pulsed multi-kilovolt bias voltage and the use of cryogenics. High voltage direct current in the multi-kilovolt range is applied to a charged circuit which may include a high voltage capacitor or use the capacitance presented by the deflection plates of the tube. The switch is laser activated and becomes photo-conducting. The charge in the capacitor passes through a charging resistor which controls the sweep rate to the deflection plates. After the activating laser pulse, the switch returns rapidly to a nonconducting state, during the recombination time of the switch material. The photo-electron beam is swept linearly over a substantial portion of the recombination time from off the image forming phosphor screen to off screen on the other side thereof. A resistor connected to the deflection plates provides a time constant long compared to the transient event lifetime, which may be the fluorescence decay time of the system under study, and the beam remains off the phosphor screen for a very large time compared to the fluorescence decay time. In a second configuration when the deflection plates are used as the charged source, the laser-activated switch is connected between a deflection plate and a point of reference potential (ground) through the charging resistor.

Femtosecond microscopy of radial energy transport in a micrometer-scale aluminum plasma excited at relativistic intensity.

Abstract: Using femtosecond microscopy, we observe subpicosecond transport of thermal energy radially outward from a micrometer-sized spot of an aluminum target following P-polarized excitation at >1018 W/cm2 with a 24 fs pulse. The rapid expansion coincides with the onset of nonlocal energy transport dominated by radiation and hot electrons.

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.