Showing papers by "Gerard Mourou published in 2015"

Fusion energy using avalanche increased boron reactions for block-ignition by ultrahigh power picosecond laser pulses

Abstract: Exceptionally high reaction gains of hydrogen protons measured with the boron isotope 11 are compared with other fusion reactions This is leading to the conclusion that secondary avalanche reactions are happening and confirming the results of high-gain, neutron-free, clean, safe, low-cost, and long-term available energy The essential basis is the unusual non-thermal block-ignition scheme with picosecond laser pulses of extremely high powers above the petawatt range

Terahertz pulse imaging in archaeology

Abstract: The work presented in this paper was performed at the Oriental Institute at the University of Chicago, on objects from their permanent collection: an ancient Egyptian bird mummy and three ancient Sumerian corroded copper-alloy objects. We used a portable, fiber-coupled terahertz (THz) time-domain spectroscopic imaging system, which allowed us to measure specimens in both transmission and reflection geometry, and present time- and frequency-based image modes. The results confirm earlier evidence that THz imaging can provide complementary information to that obtainable from X-ray computed tomography (XRCT) scans of mummies, giving better visualisation of low density regions. In addition, we demonstrated that THz imaging can distinguish mineralized layers in metal artifacts.

Plasma-based creation of short light pulses: analysis and simulation of amplification and focusing

Abstract: Plasmas can serve as damage-less optics for amplifying and focusing light pulses to very high intensity. This provides a way to overcome the limitations of solid-state optical materials as a damage threshold in the classical sense is absent. The amplification process relies on parametric processes in plasmas exploiting the coupling of transverse electromagnetic waves to a longitudinal plasma wave. The plasma response can either be an electron plasma wave (stimulated Raman scattering), an ion-acoustic wave (stimulated Brillouin scattering) or a more complicated non-resonant feature in the case of very short pulses.

Space-based application of the CAN laser to LIDAR and orbital debris remediation

Abstract: Development of pulsed lasers for space-based science missions entail many additional challenges compared to terrestrial experiments. For systems requiring short pulses ≪1 ns with energies >100 mJ and fast repetition rates >10 kHz there are currently few if no laser architectures capable of operating with high electrical efficiency >20% and have good system stability. The emergence of a mulit-channel fiber-based Coherent-Amplifying-Network or CAN laser potentially enables such capability for space based missions. Here in this article we present an analysis of two such missions scaling up in pulse energy from ≈100 mJ for a supercontinuum LIDAR application utilising atmospheric filamentation to the higher energy demands needed for space debris remediation requiring ≈10 J pulses. This scalability of the CAN laser provides pathways for development of the core science and technology where many new novel space applications can be made possible.

Petawatt laser pulses for proton-boron high gain fusion with avalanche reactions excluding problems of nuclear radiation

Abstract: An alternative way may be possible for igniting solid density hydrogen- 11 B (HB11) fuel. The use of >petawatt-ps laser pulses from the non-thermal ignition based on ultrahigh acceleration of plasma blocks by the nonlinear (ponderomotive) force, has to be combined with the measured ultrahigh magnetic fields in the 10 kilotesla range for cylindrical trapping. The evaluation of measured alpha particles from HB11 reactions arrives at the conclusion that apart from the usual binary nuclear reactions, secondary reactions by an avalanche multiplication may cause the high gains, even much higher than from deuterium tritium fusion. This may be leading to a concept of clean economic power generation.

Use of polyethylene terephthalate for temporal recompression of intense femtosecond laser pulses

Abstract: The linear characteristics of polyethylene terephthalate, such as index of refraction, spectral transmittance and transverse distribution of phase and polarization distortions, have been measured. Spectrum broadening of laser pulses (intensity over 1.3 ТW cm−2) after propagation through a 0.7 mm thick sample has been demonstrated in experiment. Taking into consideration almost unlimited aperture, submillimeter thickness and the low cost of polyethylene terephthalate, the obtained results demonstrate that it is a prospective material to be used for spectrum broadening and subsequent time compression of petawatt laser pulses to single cycle regime (Mourou et al 2014 Single cycle thin film compressor opening the door to zeptosecond-exawatt physics Eur. Phys. J. Spec. Top. 223 1181–8).

Design and properties of a coherent amplifying network laser.

Abstract: The coherent amplifying network laser is based on an array of thousands of active laser fibers coherently combined to generate high peak-power pulses at a high repetition rate. To achieve such a massive network, new combination architectures are presented here. They are based on implementing a spherical array of amplifying fibers, thus removing the need for transport fibers from the initial scheme. These designs present an advantage in terms of scalability leading to significant reduction of the temporal fluctuations compared to those of a conventional high peak-power laser. Noise evolution with fiber number is calculated using a perturbative analysis of each channel parameters (phase, signal intensity, beam profile).

XCAN – A coherent amplification network of femtosecond fiber chirped-pulse amplifiers

Abstract: The XCAN collaboration program between the Ecole Polytechnique and Thales aims at developing a laser system based on the coherent combination of several tens of laser beams produced through a network of amplifying optical fibers [1]. As a first step this project aspires to demonstrate the scalability of a combining architecture in the femtosecond regime providing high peak power with high repetition rate and high efficiency. The initial system will include 61 individual phased beams aimed to provide 10 mJ, 350 fs pulses at 50 kHz.

Extreme light - An intense pursuit of fundamental high energy physics

Abstract: By the compression of petawatt pulses to multi-exawatt, a new route for the generation of Schwinger intensities capable of producing highenergy radiation and particle beams with extremely short time structure down to the attosecond-zeptosecond regime is being presented. Far from the traditional laser investigation in the eV regime, this laser-based approach offers a new paradigm to investigate the structure of vacuum and applications to subatomic physics.

Picosecond-petawatt laser-block ignition of avalanche boron fusion by ultrahigh acceleration and ultrahigh magnetic fields

Abstract: Fusion energy from reacting hydrogen (protons) with the boron isotope 11 (HB11) resulting in three stable helium nuclei, is without problem of nuclear radiation in contrast to DT fusion. But the HB11 reaction driven by nanosecond laser pulses with thermal compression and ignition by lasers is extremely difficult. This changed radically when irradiation with picosecond laser pulses produces a non-thermal plasma block ignition with ultrahigh acceleration. This uses the nonlinear (ponderomotive) force to surprisingly resulting in same thresholds as DT fusion even under pessimistic assumption of binary reactions. After evaluation of reactions trapped cylindrically by kilotesla magnetic fields and using the measured highly increased HB11 fusion gains for the proof of an avalanche of the three alphas in secondary reactions, possibilities for an absolutely clean energy source at competitive costs were concluded.

Science and applications of the coherent amplifying network (CAN) laser

Abstract: Accelerators are today in every walk of science and life [1]. High intensity lasers drive frontiers of contemporary science. Lasers in the TW and PW regime have the potential to replace conventional accelerators with the distinct advantage to be dramatically shorter by a factor of a thousand or more [2]. For instance, electrons are accelerated to few GeV over only few centimeters, representing three to fours orders of magnitude higher accelerating gradients than traditional RF-based accelerators can offer. The approach was proposed in 1979 [3], where a strong laser pulse [4], moving in a plasma creates a wake in which electrons are trapped and violently accelerated. In addition, under ultra high intensity, high energy protons over 100 MeV have been demonstrated as well as high energy radiation greater that MeV [5]. Key to laser-driven accelerators, ion, X-Ray, or Gamma-Ray production are ultra high peak power lasers at the petawatt level [6]. However, current petawatt laser exhibits low repetition rates (state-of-the-art is about 1 Hz) due to thermo-optical character in their gain medium, resulting in low average powers in the 50 W range. In addition, a rather poor wall-plug efficiency (electrical power to optical power) of 10−3 % avoids any scaling perspectives. Hence, state-of-the-art high peak power laser system cannot pretend to be tomorrow's replacement to conventional RF Technology –a new class of ultrafast lasers is urgently needed. Under the ICFA-ICUIL [2] initiative, laser experts in the field of particle acceleration and high intensity lasers defined target parameters of a future laser system should deliver to pave the way for a new kind of accelerator technology revolutionizing fundamental science and applications. The following laser parameters are envisaged for what could be a future linear e–e+ collider: peak power in the PW regime, defined by a 10's of Joules of pulse energy and an ultrashort pulse duration below 50 fs, in combination with an unparalleled average power exceeding 100 kW even exceeding the megawatt level, implying repetition rates of >10 kHz. These extreme parameters should be contained in a beam of excellent spatial quality, featuring outstanding temporal stability and temporal contrast. An excellent wall-plug efficiency of >30% is an essential condition that such average powers are realized in a cost effective, economic and compact way. Overall, any known laser technology known today faces severe issues, with current performance orders of magnitude below these target parameters. Inspired by these ground-breaking challenges under the Eu leadership, the International Coherent Amplification Network (ICAN) group was formed. It combines the complementary expertise of science authorities in the field of high performance fiber amplifiers, theoretical and applied optics of optical systems and finally ultra high intensity lasers. ICAN aspired to study the fundamentals of interferometric amplification i.e. spatially separated amplification followed by coherent addition, of ultrashort laser pulses as the underlying concept of a breakthrough in laser physics. In detail ICAN has studied: 1) average/peak power and efficiency limits of coherently combined ultrafast laser systems 2) synchronization, spatial and temporal recombination of a large number of fibers amplifiers 3) temporal and spatial beam quality, combining efficiency of coherent addition, amplitude and phase stability as a function of the number of fibers and their individual performance 4) reduction of pulse duration and manipulation of pulse shape.