Showing papers by "Gerard Mourou published in 2020"

Fivefold compression of 250-TW laser pulses

Abstract: The pulse spectrum at the laser output was broadened due to self-phase modulation in fused silica and then the pulse was compressed by chirped mirrors. It was demonstrated that with an optimal choice of mirror dispersion a pulse with an energy of 17 J can be compressed from 70 to 14 fs. This compression after compressor approach has undoubted merits: simplicity, low cost, negligible pulse energy losses, and applicability to any high-power laser.

Thin plate compression of a sub-petawatt Ti:Sa laser pulses

Abstract: By extending the concept of thin film compression [Mourou et al., Eur. Phys. J. Spec. Top. 223(6), 1181 (2014)] to a thin plate, nonlinear post-compression from 24 fs to 13 fs of sub-petawatt laser pulses is demonstrated experimentally using a 1 mm-thick silica plate and chirped mirrors with a total anomalous dispersion of −50 fs2. The measurements were implemented with a specially designed dispersionless vacuum frequency-resolved optical gating, which is based on second harmonic generation of tested pulses in a 10 μm β-barium borate crystal glued on a 1 mm fused silica substrate. The used compression scheme is implemented in a geometry compatible with high power on-target experiment realization.

Trajectory of a flying plasma mirror traversing a target with density gradient

Abstract: It has been proposed that laser-induced relativistic plasma mirror can accelerate if the plasma has a properly tailored density profile. Such accelerating plasma mirrors can serve as analog black holes to investigate Hawking evaporation and the associated information loss paradox. Here we reexamine the underlying dynamics of mirror motion in a graded-density plasma to provide an explicit trajectory as a function of the plasma density and its gradient. Specifically, a decreasing plasma density profile (down-ramp) along the direction of laser propagation would in general accelerate the mirror. In particular, a constant-plus-exponential density profile would generate the Davies-Fulling trajectory with a well-defined analog Hawking temperature, which is sensitive to the plasma density gradient but not to the density itself. We show that without invoking nano-fabricated thin-films, a much lower density gas target at, for example, $\sim 1\times 10^{17}{\rm cm}^{-3}$, would be able to induce an analog Hawking temperature, $k_{_B}T_{_H}\sim 6.6 \times 10^{-2}{\rm eV}$, in the far-infrared region. We hope that this would help to better realize the experiment proposed by Chen and Mourou.

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.

Trajectory of a flying plasma mirror traversing a target with density gradient

Abstract: It has been proposed that laser-induced relativistic plasma mirror can accelerate if the plasma has a properly tailored density profile. Such accelerating plasma mirrors can serve as analog black holes to investigate Hawking evaporation and the associated information loss paradox. Here we reexamine the underlying dynamics of mirror motion in a graded-density plasma to provide an explicit trajectory as a function of the plasma density and its gradient. Specifically, a decreasing plasma density profile (down-ramp) along the direction of laser propagation would in general accelerate the mirror. In particular, a constant-plus-exponential density profile would generate the Davies-Fulling trajectory with a well-defined analog Hawking temperature, which is sensitive to the plasma density gradient but not to the density itself. We show that without invoking nano-fabricated thin-films, a much lower density gas target at, for example, $\sim 1\times 10^{17}{\rm cm}^{-3}$, would be able to induce an analog Hawking temperature, $k_{_B}T_{_H}\sim 6.6 \times 10^{-2}{\rm eV}$, in the far-infrared region. We hope that this would help to better realize the experiment proposed by Chen and Mourou.

First HPLS Experiments at ELI-NP: Spectral Broadening in Thin Films

Abstract: Following the completion of the installation and testing of the HPLS 2x10PW laser system at ELI-NP, prospective experiments related to spectral broadening in thin films for post-compression were performed at the HPLS 100TW output.

Cascaded Generation of a Sub-10-Attosecond Half-Cycle Pulse.

Abstract: Sub-10-attosecond pulses with half-cycle electric fields provide exceptional options to detect and manipulate electrons in the atomic timescale. However, the availability of such pulses is still challenging. Here, we propose a method to generate isolated sub-10-attosecond half-cycle pulses based on a cascade process naturally happening in plasma. A 100s-attosecond pulse is first generated by shooting a moderate overdense plasma with a one-cycle femtosecond pulse. After that, the generated attosecond pulse cascadedly produce a sub-10-attosecond half-cycle pulse in the transmission direction by unipolarly perturbing a nanometer-thin relativistic electron sheet naturally form in the plasma. Two-dimensional particle-in-cell simulations indicate that an isolated half-cycle pulse with the duration of 8.3 attoseconds can be produced. Apart from one-cycle driving pulse, such a scheme also can be realized with a commercial 100-TW 25-fs driving laser by shaping the pulse with a relativistic plasma lens in advance.

Progress towards a LWFA-based X-ray machine for plant phase-contrast X-ray imaging

Abstract: We present a review of INRS program on intense X-ray sources based on laser wake-field acceleration for high throughput plant imaging. Key technical points to achieve the best compromise between complexity and performance are discussed.