Showing papers by "Gerard Mourou published in 2001"
TL;DR: A self-starting Kerr-lens mode-locked Yb:KY(WO(4))(2) laser directly end pumped by two 1.6-W diodes is demonstrated for what is to the authors' knowledge the first time.
Abstract: A self-starting Kerr-lens mode-locked Yb:KYWO42 laser directly end pumped by two 1.6-W diodes is demonstrated for what is to our knowledge the first time. Pulses as short as 71 fs with 120-mW average output power, at a center wavelength of 1057 nm, were obtained at a repetition rate of 110 MHz. A 10-nm tuning range was achieved with longer pulses and higher average output power.
203 citations
TL;DR: In this article, the authors observed deuterons accelerated to energies of about 2 MeV in the interaction of relativistically intense 10 TW, 400 fs laser pulse with a thin layer of deuterated polystyrene deposited on Mylar film.
Abstract: We have observed deuterons accelerated to energies of about 2 MeV in the interaction of relativistically intense 10 TW, 400 fs laser pulse with a thin layer of deuterated polystyrene deposited on Mylar film. These high-energy deuterons were directed to the boron sample, where they produced ∼105 atoms of positron active isotope 11C from the reaction 10B(d,n)11C. The activation results suggest that deuterons were accelerated from the front surface of the target.
175 citations
TL;DR: The design of an autocorrelator is shown that can be used to eliminate the pulse-front tilt and simultaneously adjust the pulse duration in real time by adjustment of the pulse compressor of a chirped-pulse amplified laser system.
Abstract: We present a method of adjusting the pulse duration and eliminating the pulse-front tilt of an ultrashort pulse in real time by use of a specially configured single-shot autocorrelator. Pulse-front tilt, or a temporal delay across the pulse front, is a common ultrashort-pulse phenomenon when dispersive elements are being used. We show the design of an autocorrelator that can be used to eliminate the pulse-front tilt and simultaneously adjust the pulse duration in real time by adjustment of the pulse compressor of a chirped-pulse amplified laser system.
79 citations
Patent•
08 Nov 2001
TL;DR: In this paper, a system for generating high-energy particles and for inducing nuclear reactions is described, which includes a laser and for emitting a laser beam, an irradiation target for receiving the laser beam and producing high energy particles, and a secondary target to receive the high energy particle and thereby inducing a nuclear reaction.
Abstract: A system is provided for generating high-energy particles and for inducing nuclear reactions The system includes a laser and for emitting a laser beam, an irradiation target for receiving the laser beam and producing high-energy particles, and a secondary target for receiving the high-energy particles, thereby inducing a nuclear reaction A method is also provided including producing a laser beam of high-intensity with an ultra-short pulse duration, irradiating the laser beam onto an irradiation target in order to ionize the irradiation target and produce a collimated beam of high-energy particles, and colliding the collimated beam of high-energy particles onto a secondary target containing a nuclei, thereby inducing a nuclear reaction on the secondary target
57 citations
TL;DR: The spectral phase interferometry for direct electric field reconstruction is used to characterize the pulse temporally and correct the spectral phases of amplified femtosecond pulses by using a deformable mirror in the stretcher.
Abstract: We correct the spectral phases of amplified femtosecond pulses by using a deformable mirror in the stretcher. After the correction the peak intensity is multiplied by 1.5 as a consequence of increasing the contrast by 100×. The spectral phase interferometry for direct electric field reconstruction is used to characterize the pulse temporally.
25 citations
01 Jan 2001
TL;DR: Achlioptas et al. as mentioned in this paper proposed the chirped pulse amplification (CPA) technique, which can achieve an optical field strength greater than 1021 W/cm2, one million times greater than previously possible.
Abstract: Today laser optics stands on the threshold of a new frontier of unprecedented optical field strengths with single-cycle pulse durations. Traditional optics concerns physical phenomena in the eV regime. The new frontier will address GeV energy scales. In the last decade, lasers have undergone orders-of-magnitude jumps in peak power, with the invention of the technique of chirped pulse amplification (CPA) and refinement of femtosecond techniques. Modern CPA lasers can produce intensities greater than 1021 W/cm2, one million times greater than previously possible. Above 1018W/cm2, an electron oscillating in the optical frequency laser field has a peak velocity approaching the speed of light, c. and the laser field exceeds many TV/m, fields greater than any other technology can muster. Under these conditions, relativistic nonlinearities emerge. The relativistic intensity regime is rich in novel physical effects, including acceleration of electrons and ions to multi-MeV energies, vacuum heating at surfaces, relativistic harmonic generation from free electrons, relativistic self-focusing and transparency. These ultra-intense lasers give researchers a tool to produce unprecedented pressures —Tbars, magnetic fields-Gigagauss-, temperatures — 1010 K- and accelerations- 1025g-with applications to fusion energy, nuclear physics, high energy physics, astrophysics and cosmology
16 citations
TL;DR: In this article, the laser intensity threshold for pion production by protons accelerated by relativistically strong short laser pulses acting on a solid target was determined as a function of laser intensity.
Abstract: Two-dimensional “particle-in-cell” modeling was carried out to determine the laser intensity threshold for pion production by protons accelerated by the relativistically strong short laser pulses acting on a solid target. The pion production yield was determined as a function of laser intensity.
16 citations
TL;DR: In this article, the design and performance of a high-energy large-mode regenerative amplifier for chirped-pulse amplification is described, and a one-amplifier terawatt laser is feasible on the basis of this design.
Abstract: We report on the design and performance of a high-energy large-mode regenerative amplifier for chirped-pulse amplification. Output energy up to 90 mJ and slope efficiency of 37% are demonstrated. A one-amplifier terawatt laser is feasible on the basis of this design.
13 citations
04 May 2001
TL;DR: Complete subsurface incisions in human sclera are demonstrated by selecting a laser wavelength that is focusable beneath the surface, namely 1700 nm and similar techniques may be used in other translucent tissues such as skin.
Abstract: Approximately 5 million people worldwide are blind due to complications from glaucoma, and an estimated 105 million have the disease. Current surgical techniques often fail due to scarring that is associated with disruption of the ocular surface tissues using conventional surgical methods. Demonstrated in the transparent cornea, femtosecond lasers can create a highly precise incision beneath the surface of a tissue. Since sclera is highly scattering with one micron light, the same wavelength used in cornea cannot be focused to the small spot necessary for photodisruption far beneath the surface of sclera. We now demonstrate completely subsurface incisions in human sclera by selecting a laser wavelength that is focusable beneath the surface, namely 1700 nm. Similar techniques may be used in other translucent tissues such as skin. Subsurface femtosecond photodisruption may be a useful for in vivo surgical technique to perform a completely subsurface surgery.
9 citations
Patent•
29 Nov 2001
TL;DR: In this article, the authors proposed a method by which a structure of non-biological material is accurately localized and cut with a pulse laser beam by focusing the attention upon the fact that the feature of the material is seen in a rapid and decisive variation of the gradient occurring in a constant pulse width value in the relation between the fluence breaking threshold value Fth and the width T of the laser beam pulse.
Abstract: PROBLEM TO BE SOLVED: To provide a method by which a structure of non-biological material is accurately localized and cut with a pulse laser beam. SOLUTION: By focusing the attention upon the fact that the feature of the material is seen in a rapid and decisive variation of the gradient occurring in a constant pulse width value in the relation between the fluence breaking threshold value Fth and the width T of the laser beam pulse, the method comprises a process in which the laser beam, each pulse width of which is equal to the constant laser pulse width or smaller, is generated and the material is irradiated with the laser beam.
7 citations
28 Jan 2001
TL;DR: In this paper, the use of a new crystal, Yb:GdCOB, for the development of a regenerative amplifier was reported, which was used in a CPA system.
Abstract: We report the use of a new crystal: Yb:GdCOB for the development of a regenerative amplifier. This amplifier used in a CPA system generates 21-mJ pulses with a bandwidth of 8-nm leading to 350-fs, 12-mJ pulses after compression.
11 May 2001
TL;DR: In this article, the first self-starting mode-locked Yb/sup 3+/:KY(WO/sub 4/)/sub 2/ (Yb:KYW) laser based on Kerr-lensing effect was presented.
Abstract: Summary form only given. We present what is, to our best knowledge, the first self-starting mode-locked Yb/sup 3+/:KY(WO/sub 4/)/sub 2/ (Yb:KYW) laser based on Kerr-lensing effect. The 10-at.% Yb/sup 3+/-doped KY(WO/sub 4/)/sub 2/ crystal is 4-mm long with Brewster angle for the E//b signal beam and is cooled to 18/spl deg/C. The gain material is CW end-pumped by two 100 /spl mu/m stripe laser diodes operating at 940 nm with a spectral bandwidth of /spl sim/3 nm FWHM. One of these diodes is slightly damaged and its light is focused to a beam diameter of 120 /spl mu/m/spl times/30 /spl mu/m (1/e/sup 2/ intensity) with 1.25 W reaching the crystal. The light of the other diode is focused to a beam diameter of 110 /spl mu/m/spl times/30 /spl mu/m (1/e/sup 2/ intensity) with 1.35 W reaching the crystal. Over 90% pump light is absorbed and we obtain 580 mW CW output power with a 2% output coupler without prisms in the cavity.
TL;DR: In this paper, the use of a new crystal, Yb:GdCOB, for the development of a regenerative amplifier was reported, which generated 21mJ pulses with a bandwidth of 8 nm.
11 May 2001
TL;DR: In this paper, an unbalanced nonlinear Sagnac interferometer was used to detect the presence of an amplified spontaneous emission (ASE) background coming from the amplification process.
Abstract: Summary form only given. The development of laser chains based on the chirped pulse amplification leads now to peak powers higher than 100 TW. The focused intensity can reach 10/sup 21/ W/cm/sup 2/. To keep the laser matter interaction in the femtosecond regime, the pulse has to exhibit a high temporal contrast. The most important problem consists in the presence of an amplified spontaneous emission (ASE) background coming from the amplification process. At the output of the laser the ratio between the femtosecond pulse intensity and the ASE level is about 10/sup 6/ leading to an ASE intensity as high as 10/sup 15/ W/cm/sup 2/, far above the ionization threshold of most materials and susceptible to strongly modify the interaction process. We propose to rely on an unbalanced nonlinear Sagnac interferometer which is implemented after the first CPA system amplifies pulses to the millijoule level.
11 May 2001
TL;DR: In this paper, a ring resonator with an intracavity lens was used in a high-energy/large-mode regenerative amplifier as such a cavity has a larger mode size compared with a linear one with the same footprint.
Abstract: Summary form only given. A typical meter size linear Ti:sapphire regenerative amplifier has submillimeter mode size and output energy of 1-10 mJ limited by saturation fluence of Ti:sapphire (0.9j/cm/sup 2/) and intracavity losses. Subsequent amplification to joule scale energy requires a saturated gain of 100-1000 which is hard to reach with a single multipass amplifier so multiple stages of multipass amplifiers are used resulting in beam quality degradation and overall complexity of the laser system. A ring resonator with an intracavity lens was used in a high-energy/large-mode regenerative amplifier as such a cavity has a larger mode size compared with a linear one with the same footprint. However, for broadband 20-30 femtosecond lasers, only reflective optics can be used to avoid chromatic aberrations.
21 Oct 2001
TL;DR: By focusing 1 mJ, 21 fs pulses to a 1.6 μm spot on solid Cu and Ge targets, x-ray line emission around 10 keV photon energy was produced with a 7 μm source size.
Abstract: By focusing 1 mJ, 21 fs pulses to a 1.6 μm spot on solid Cu and Ge targets, x-ray line emission around 10 keV photon energy was produced with a 7 μm source size.
01 Dec 2001
TL;DR: In this article, the authors proposed the use of chirped pulse amplification (CPA) and the refinements of femtosecond techniques to achieve a peak power of 10 21 W/cm 2, one million times greater than previously possible.
Abstract: Traditional optics and nonlinear optics are related to laser–matter interaction with eV characteristic energy. Recent progresses in ultrahigh intensity makes it possible to drive electrons with relativistic energy opening up the field of relativistic nonlinear optics. In the last decade, lasers have undergone orders-of-magnitude jumps in peak power, with the invention of the technique of chirped pulse amplification (CPA) and the refinements of femtosecond techniques. Modern CPA lasers can produce intensities greater than 10 21 W/cm 2 , one million times greater than previously possible. These ultraintense lasers give researchers a tool to produce unprecedented pressures (terabars), magnetic fields (gigagauss), temperatures (10 10 K), and accelerations (10 25 g) with applications in fusion energy, nuclear physics (fast ignition), high-energy physics, astrophysics, and cosmology. They promote the optics field from the eV to the GeV.
18 Jun 2001
TL;DR: In this article, a collimated beam of fast protons, produced by a 10TW laser with frequencies of either 1.053 micron light or 2/spl omega/sub 0/ (corresponding to 532 nm light) focused to an intensity of more the 3/spl times/10/sup 19/ W/cm/sup 2/ onto the surface of a thin-film target.
Abstract: We have conducted investigations of a collimated beam of fast protons, produced by a 10TW laser with frequencies of either /spl omega//sub 0/ (corresponding to 1.053 micron light) or 2/spl omega//sub 0/ (corresponding to 532 nm light) focused to an intensity of more the 3/spl times/10/sup 19/ W/cm/sup 2/ onto the surface of a thin-film target. Energies as high as 10 MeV and total number of 10/sup 9/, confined in a cone angle of 40/spl deg//spl plusmn/10/spl deg/ have been observed. The protons, which originate form impurities on the front side of the target and exit out the backside in a direction normal to the target surface. Acceleration field gradients of /spl sim/10 GeV/cm have been inferred. The maximum proton energy for 2/spl omega//sub 0/ can be explained by the charge-separation electrostatic-field acceleration due to "vacuum heating". In another set of experiments when a deuterated polystyrene layer was deposited on a surface of a Mylar film and a /sup 10/B sample was placed behind the target, we observed the production of /spl sim/10/sup 5/ atoms of positron active isotope /sup 11/C from the nuclear fusion reaction /sup 10/B(d,n)/sup 11/C. No activation was detected when only the proton beam was used. We also discuss the use of ions from these table-top sources for medical applications such as cancer radiotherapy and fundamental studies in radio-biology.
11 May 2001
TL;DR: In this paper, the first Yb:GdCOB regenerative chirped pulse amplification system was presented to produce 12-mJ and 350-fs pulses with high repetition rate.
Abstract: Summary form only given. In this summary, we present the first Yb:GdCOB regenerative chirped pulse amplification system to produce 12-mJ, and 350-fs pulses. We have extracted reasonable amount of energy from Yb:GdCOB. If we employ a diode-pumping scheme, we could obtain hundreds, of milli-joule pulses with high repetition rate.
11 May 2001
TL;DR: In this paper, the electron diffraction technique is used to directly study electron-phonon coupling in the femtosecond time scale using the Debye-Waller effect and surface dynamics.
Abstract: Summary form only given. Twenty years ago, the technique of electron diffraction was introduced and made for the first time possible the direct observation of structural changes in the picosecond time scale. This simple technique is based on the photoelectric effect and provides a perfectly synchronized electron "replica" of the incident pulse. The technique was originally demonstrated with a 20 picosecond resolution and was used to investigate the dynamic of melting. Later it was used at the 100 ps level to investigate surface melting. The technique was further pushed to the subpicosecond time scale to study light induced chemical reactions in gas phase. At the University of Michigan the electron diffraction technique is used to directly study electron-phonon coupling in the femtosecond time scale using the Debye-Waller effect and surface dynamics. We show the experimental set up of the electron diffraction system and give results for a [111] transmission electron diffraction pattern of a 30 nm thick gold single crystal.
11 May 2001
TL;DR: In this paper, it was shown that single millijoule pulses in the 10-fs regime (single cycle), focused to 1-spl mu/m (single wavelength), can produce intensities greater than 10/sup 19/ W/cm/sup 2/ at kilohertz repetition rates.
Abstract: Summary form only given. Laser intensity in the relativistic regime, i.e. > 10/sup 18/ W/cm/sup 2/ for near-IR light, has opened new frontiers in physics. At this intensity, electrons acquire quiver energy greater than, 0.5 MeV, corresponding to the mass-energy of the electron. Their relativistic behavior is dominated by a mass increase and a large ponderomotive force (v /spl times/ B) where v is the quiver velocity of the electrons and B the light magnetic field. The laser-matter interaction in this regime is characterized by the generation of high-energy photons (x-rays and /spl gamma/-rays) and energetic electrons and ion. The latter are accelerated to tens of MeVs by the large forces associated with the v /spl times/ B term. Recently, we have shown that single millijoule pulses in the 10-fs regime (single cycle), focused to 1-/spl mu/m (single wavelength), can produce intensities greater than 10/sup 19/ W/cm/sup 2/ at kilohertz repetition rates. Because of their very short Rayleigh range (/spl sim/1 /spl mu/m) one might think that these pulses would have only limited applications. They would not be useful in electron acceleration, where longer interaction distances are necessary. If the laser numerical aperture (NA) is matched to the NA of a relativistic waveguide (determined by the laser power and the plasma frequency), single-mode propagation of the relativistic pulse over many Rayleigh ranges can be obtained, as in conventional waveguide optics. This is demonstrated by a 2D PIC simulation of laser pulse matching with a plasma slab.
12 Mar 2001
TL;DR: In this paper, a deuterated polystyrene was deposited on the front surface of the film and a boron sample was placed behind the target, and the activation results suggest that ions (protons and deuterons) were accelerated from the front surfaces of the target.
Abstract: The protons with the energy up to 10 MeV accelerated in the forward direction from the thin Mylar film by relativisticallyintense 10 TW, 400 fs laser pulse have been observed. When a deuterated polystyrene was deposited on the front surface ofthe film and a boron sample was placed behind the target the production of i05 atoms of positron active isotope "C from thereaction 1°B(d,n)'1C have been measured. The activation results suggest that ions (protons and deuterons) were acceleratedfrom the front surface of the target.Keywords: high-intensity laser, high-energy ions, activation technique, radioisotope 1. INTRODUCTION Since their invention more than sixty years ago cyclotrons' have been the standard method used to accelerate protons andions for experiments in nuclear physics and applications in nuclear medicine. The development of short-pulse high-intensitylasers1 made it possible to accelerate protons and heavier ions to multi-MeV energies in the interaction of these lasers withsolid targets25 gas jets6 and clusters.7 Unlike traditional sources that generate proton pulses longer than several nanoseconds,the laser acceleration technique allows one to generate pulses that are a few orders of magnitude shorter with a peak current
11 May 2001
TL;DR: In this article, it was shown that 10/sup 19/W/cm/sup 2/ can be produced with a high repetition rate laser, which is much more stable and compact than the low repetition rate lasers.
Abstract: Summary form only given. The relativistic nonlinear optics is a fundamentally new optical regime, where the product of the laser intensity times the square of the wavelength exceeds /spl sim/10/sup 18/ (W/cm/sup 2/)/spl mu/m/sup 2/. In the last few years, laser-matter interaction at relativistic laser intensity has been studied extensively, which lead to the demonstration of many new phenomena such as relativistic self-focusing, nonlinear Thomson scattering and MeV particle acceleration. These experiments, however, were done with low-repetition-rate/single-shot lasers. In a previous paper, we demonstrated for the first time that relativistic intensity pulses could be generated at 1 kHz repetition rate. In this paper, we showed that 10/sup 19/W/cm/sup 2/ can be produced with a high repetition rate laser, which is much more stable and compact than the low repetition rate lasers.
15 Jul 2001
TL;DR: In this paper, the first Yb:KY(WO/sub 4/)/sub 2/ regenerative amplifier was presented, which is, to the best of our knowledge, the only one known to exist.
Abstract: Summary form only given. We present what is, to our best knowledge, the first Yb:KY(WO/sub 4/)/sub 2/ (Yb:KYW) regenerative amplifier. The 10-at.% Yb/sup 3+/-doped KY(WO/sub 4/)/sub 2/ crystal is 4-mm long and cut at Brewster angle for the E//b signal beam. The injection pulses originated from a directly diode-pumped Yb:glass saturable-absorber mode-locked oscillator. The mode-locked pulses stretched by a grating stretcher before being injected.
11 May 2001
TL;DR: In this paper, the angular distribution of isotope enrichments and the dependence on laser parameters and on the atomic-transport mean free path between collisions were examined as a function of ion energy, ion charge state, and atomic mass.
Abstract: Summary form only given. It has been observed that isotopic enrichment of light ions occurs in the central portion of laser ablation plumes when such plasmas are formed with ultrafast laser pulses. It was found that the separation of lighter isotopes from heavier isotopes occurs on axis in the expanding plasma plume. The relative independence of the enrichment on axis among different elements and other similarities in the ion distributions have indicated a universality to this effect that lends credence to a possible plasma centrifuge model. In the present work, we examine the angular distribution of isotope enrichments and investigate the dependence on laser parameters and on the atomic-transport mean free path between collisions. The angular dependence is studied as a function of ion energy, ion charge state, and atomic mass.
TL;DR: By focusing 21-fs laser pulses down to a 1.6-µm spot with aberration compensated optics, this article demonstrated that a peak intensity of 4x1018 W/cm2 can be produced at 300-Hz repetition rate.
Abstract: By focusing 21-fs laser pulses down to a 1.6-µm spot with aberration- compensated optics, we demonstrated for the first time that a peak intensity of 4x1018 W/cm2 can be produced at 300-Hz repetition rate.