Cavity-enhanced similariton Yb-fiber laser frequency comb: 3 x 10(14) W/cm2 peak intensity at 136 MHz

We report on a passive cavity-enhanced Yb-fiber laser frequency comb generating 230 MW of peak power (3 kW of average power) at a 136 MHz pulse repetition rate. The intracativy peak intensity of 3 x 10(14) W/cm2 for the 95 fs pulse is sufficient to ionize noble gases, such as Xe, Kr, or Ar. The laser system is based on a mode-locked Yb-fiber similariton oscillator in conjunction with a cladding-pumped chirped-pulse fiber amplifier. After recompression, 75 fs duration pulses at a 13.1 W average power are obtained. These pulses are then coherently added inside a passive ring cavity by controlling the fiber oscillator's pulse repetition rate and carrier-envelope offset frequency. This system is well suited for studying high-field phenomena at very high pulse repetition rates.     

Neutron production in a picosecond laser plasma at a radiation intensity of 3×1017W/cm2

Neutron production as a result of the reaction ²H(d, n)³He in a picosecond laser plasma is reported. A considerable neutron yield of 5×10⁴ per pulse is obtained for the first time in a picosecond laser plasma on the surface of a solid deuterated target at laser radiation intensity of 3×10¹⁷ W/cm².     

Continuous-wave mode-locked Ti:sapphire laser focusable to 5 x 10(13) W/cm(2)

Generation of sub-10-fs pulses with an average power of 1 W and a peak of 1.5 MW from a Kerr-lens mode-locked mirror-dispersion-controlled Ti:sapphire laser is demonstrated. A specially designed lens triplet focuses the output of this compact all-solid-state source to a peak intensity in excess of 5x10(13) W/cm (2) . Nonperturbative nonlinear optics is now becoming feasible by use of the output of a cw mode-locked laser.     

Generation and characterization of the highest laser intensities (10(22) W/cm2)

We generated a record peak intensity of 0.7 x 10(22) W/cm2 by focusing a 45-TW laser beam with an f/0.6 off-axis paraboloid. The aberrations of the paraboloid and the low-energy reference laser beam were measured and corrected, and a focal spot size of 0.8 microm was achieved. It is shown that the peak intensity can be increased to 1.0 x 10(22) W/cm2 by correction of the wave front of a 45-TW beam relative to the reference beam. The phase and amplitude measurement provides for an efficient full characterization of the focal field.     

Dominance of radiation pressure in ion acceleration with linearly polarized pulses at intensities of 10(21) W cm(-2)

A novel regime is proposed where, by employing linearly polarized laser pulses at intensities 10(21) W cm(-2) (2 orders of magnitude lower than discussed in previous work [T. Esirkepov et al., Phys. Rev. Lett. 92, 175003 (2004)]), ions are dominantly accelerated from ultrathin foils by the radiation pressure and have monoenergetic spectra. In this regime, ions accelerated from the hole-boring process quickly catch up with the ions accelerated by target normal sheath acceleration, and they then join in a single bunch, undergoing a hybrid light-sail-target normal sheath acceleration. Under an appropriate coupling condition between foil thickness, laser intensity, and pulse duration, laser radiation pressure can be dominant in this hybrid acceleration. Two-dimensional particle-in-cell simulations show that 1.26 GeV quasimonoenergetic C(6+) beams are obtained by linearly polarized laser pulses at intensities of 10(21) W cm(-2).     

Particular features of the transmission of laser radiation with wavelength 0.438 µm and intensity (3–7)·1014 W/cm2 through an undercritical plasma from polymer aerogels

The velocities of energy transport in an undercritical plasma of polymer aerogel with and without copper nanoparticles were measured. Transmission of the laser light through targets of different thicknesses such as submicron three-dimensional polymer networks with densities below the critical value (0.13–0.52 N _cr) for a wavelength of 0.438 μm and intensity of (3–7)·10¹⁴ W/cm² at a half-height pulse duration of 0.32 ns was studied. The transfer of a heating laser radiation was registered on the rear side of the target. It ranged from a level of ∼0.5% for the thickness of a low-density layer of 400 μm and density of 9 mg/cm³ (mass per unit square of 0.36 mg/cm²) up to 50–60% for a thickness of 100 μm and density of 2.25 mg/cm³ (mass per unit square of 0.02 mg/cm²). The time dependences of the optical emission from the rear side of the targets were measured. They appear to be indicative of the plasma dynamics in two-layer targets (polymer foam on Al foil) and enable the estimation of the absorption depth for the laser light in an undercritical plasma. __________ Translated from Preprint No. 8 of the P. N. Lebedev Physical Institute, Moscow (2007).     

Characterization of focal field formed by a large numerical aperture paraboloidal mirror and generation of ultra-high intensity (1022 W/cm2)

We describe a method to measure the aberrations of a high numerical aperture off-axis paraboloid and correct for the aberrations using adaptive optics. It is then shown that the characterized aberrations can be used to accurately calculate the electromagnetic field at the focus using the Stratton–Chu vector diffraction theory. Using this methodology, an intensity of 7×10²¹ W/cm² was demonstrated by focusing a 45-TW laser beam with an f/0.6, 90^∘ off-axis paraboloid after correcting the aberrations of the paraboloid and the low-energy reference beam. The intensity can be further increased to 1×10²² W/cm² by including in the correction algorithm the wavefront difference between the reference beam and the high-energy beam. This revised version was published online in May 2005. The authors addresses were completed PACS numbers were added Equation (31) was corrected Textual corrections were made in Sects. 3, 4.1, and 5 Reference no. 12 was completed. An erratum to this article can be found at .     

Relativistic MeV photoelectrons from the single atom response of argon to a 10 19 W/cm2 laser field

We present photoelectron measurements from argon ionization at 10(19) W/cm(2). Photoelectrons with energies above 400 keV, including a 1.2 MeV cutoff, are in quantitative agreement with a semiclassical, relativistic 3D ionization model that includes a nonparaxial laser field. L-shell photoelectrons have energies and momentum dominated by the field, including the acceleration out of the focus. Yields and angular distributions at 60 keV come from valence shell ionization by strong fields where rescattering and atomic processes determine photoelectron final states.     

Rayleigh-Taylor growth stabilization in direct-drive plastic targets at laser intensities of approximately 1 x 10(15) W/cm2

Direct-drive, planar-target Rayleigh-Taylor growth experiments were performed for the first time to test fundamental physics in hydrocodes at peak drive intensities of ignition designs. The unstable modulation growth at a drive intensity of approximately 1 x 10(15) W/cm2 was strongly stabilized compared to the growth at an intensity of approximately 5 x 10(14) W/cm2. The experiments demonstrate that standard simulations based on a local model of electron thermal transport break down at peak intensities of ignition designs (although they work well at lower intensities). The preheating effects by nonlocal electron transport and hot electrons were identified as some of the stabilizing mechanisms.     

Production of intensities of ∼ 1019 W/cm2 by a table-top KrF laser

We report on the generation of intensities of 10¹⁹ W/cm^–2 by focusing the output beam of a table-top hybrid dye-excimer laser system operating at 248 nm. The laser system uses a pulsed dye laser and a single, commercially available excimer gain module. Considerations and optical arrangements for the optimization of the phase-front and the beam homogeneity of ultraviolet excimer amplifiers are presented.Prof. F.P. Schäfer on the occasion of his 65th birthday.     

Guiding and high-harmonic generation of sub-10-fs pulses in hollow-core fibers at 1015 W/cm2

15 W/cm². The high resistance of fused silica to damage in the sub-10-fs regime allows stable reproducible operation without degradation of the capillary waveguide. In preliminary experiments, we demonstrate kHz-repetition-rate guided-wave high-harmonic generation in helium down to the 10-nm range. The reported experiments open up the way to realizing high-field interactions with plane-wave excitation at intensity levels in excess of 10¹⁵ W/cm² under well-controlled conditions. Received: 28 May 1998     

Focusing all the synchrotron radiation (2π radians) from an electron storage ring on a single point without time distortion

The geometrical-optical analysis of synchrotron radiation shows that it is possible to define a mirror able to focus all the emitted light by an electron storage ring on a single point lying anywhere in space, keeping unchanged the typical time patterns of the radiation. Because of the electron ultrarelativistic conditions, the electron “orbital path” is assimilated to an “underground bent photon path”. We prove then that the focusing condition is simply given by establishing the invariance of the photon path: “optical photon path” + “underground bent photon path” = constant. Some selected numerical examples show that it is possible to collect huge amounts of radiation producing extremely high excitation densities in a given small volume.     

Optical Harmonics Generation under the Interaction of Intense (up to 1014 W/cm2) Mid-Infrared Femtosecond Laser Radiation of a Fe:ZnSe Laser System with a Dense Laminar Gas Jet

JETP Letters - Low-order (fifth, seventh, and ninth) harmonics have been generated under the interaction of intense (I ~ 1014 W/cm2) femtosecond mid-infrared radiation of a laser...     

Hard X radiation and fast particles in laser plasma experiments at laser intensities of up to 5×1018 W/cm2 on the target surface

Results are presented from an investigation of the hard X-ray spectrum and the parameters of fast particles in experiments on the interaction of laser pulses with solid targets in the PROGRESS-P facility at laser intensities of up to 5×10¹⁸ W/cm² on the target surface. The maximum energy of fast electrons obtained from direct measurements is found to be 8–10 MeV.     

Structural and optical properties of high-density (>10/cm) InAs QDs with varying Al(Ga)As matrix layer thickness

We have obtained high-density (>10¹¹/cm²) InAs quantum dot (QD) structures by using an Al(Ga)As matrix layer. With increase of the AlAs matrix layer thickness, the density of QDs increases a little and the luminescence intensity emitted from InAs QDs decreases. We have used a thin GaAs insertion layer (IL) for the reason of keeping InAs QDs from an aluminum intermixing towards QDs. As the thickness of GaAs IL increases, the density of QDs decreases slightly due to the reduction of the roughness of an AlAs matrix layer. However, the luminescence intensity increases with increase in the thickness of GaAs IL resulting from the efficient blocking of an aluminum intermixing towards QDs.     

Spontaneous emission of an ensemble of 57Fe nuclei interacting with a coherent radiation field coupling the Zeeman sublevels of a nuclear excited 3/2 state

The concept “dressed nucleus” is introduced to describe the interaction of a nucleus (in a static magnetic field) with a coherent radiation field at resonance with the Zeeman sublevels. The idea is to consider the global system as a one quantum system in the Schrödinger representation. It is shown that it is possible to associate to each nuclear Zeeman substate an infinite number of equidistant energy levels, each of them having a four-fold degeneracy when any interaction with the coherent field is neglected. This periodic energy scheme, which is the same for any nuclear Zeeman substate, is a consequence of the resonance condition and of the specific form of the coherent state of the radiation field. When the interaction is included the energy degeneracy is lifted and each level splits into (2I+1)² equidistant levels, where I is the spin of the free nuclear state. The energy difference between two adjacent levels is proportional to the square root of the mean photon number in the coherent state. When the global system decays spontaneously to a possible ground state a \gamma-photon is produced. Taking into account the selection rules 24 different \gamma-energies are possible for a nuclear M1 3/2→1/2 transition.     

Nonlinear-photonics devices on the basis of the coherent interaction of optical radiation with resonant media (a review)

We have examined examples of nonlinear-photonics devices that are based on the coherent interaction of light with matter. Such interaction takes place if the duration of a light pulse is shorter than the relaxation times T ₁ and T ₂ in a resonant medium and if the strength of the light field is so high that Rabi oscillations arise. Theoretical analysis shows that these systems have a number of advantages compared to similar devices that operate under incoherent interaction conditions of light with matter.     

Excitation of 2D plasmons in a Cs/W(110) system

The evolution of surface photoemission spectra was investigated for a Cs/W(110) system with metastable Cs coatings larger than a monolayer. It is demonstrated that 2D plasmons can be detected by threshold photoemission spectroscopy. Three photoemission peaks were observed, whose dependence on the Cs adsorption dose showed a complicated behavior. The peaks may be due to the photoinduced excitation of a plasmon in quasi-2D Cs clusters, a surface Cs plasmon, or an interface Cs-W plasmon.