Michael Geissler

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).

Phase sensitivity of high-order harmonic generation with few-cycle laser pulses

We have theoretically investigated the phase dependence of high-harmonic generation with few-cycle laser pulses. We performed the analysis by solving the coupled evolution equations for the laser pulse and for the harmonic field in one space dimension. Our calculations reveal phase-dependent features in the cutoff region, such as a phase-dependent shift of the cutoff, that are preserved during propagation.

Effects of external axial magnetic field on fast electron propagation

A scheme employing an external axial magnetic field is proposed to diagnose the intrinsic divergence of laser-generated fast electron beams, and this is studied numerically with hybrid simulations. The maximum beam radius of fast electrons increases with the initial divergence and decreases with the amplitude of the axial magnetic field. It is indicated that the intrinsic divergence of fast electrons can be inferred from measurements of the beam radius at different depth under the axial field. The proposed scheme here may be useful for future fast ignition experiments and in other applications of laser-generated fast electron beams.

Relativistic plasma-wave pulse-compression

Summary form only given. With current techniques, using the Kerr nonlinearity of a gas filled hollow fiber together with chirped mirrors, sub-10 fs pulses with a maximum peak intensity of I/spl ap/10/sup 17/ W/cm/sup 2/ can be achieved after tight focusing. It is not possible to extend this pulse compression technique to higher pulse energies because of the onset of fiber damage. However guiding is essential to eliminate transverse pulse distortion and to achieve long interaction distances necessary for pulse compression. Therefore, we propose to use, instead of a hollow waveguide, a plasma-channel which can be preformed or can be generated by self-channeling. The advantage of a plasma channel is that guiding of laser pulses with unlimited pulse energies and peak intensities is possible. Our numerical (1D-PIC) analysis indicates that, similar to the Kerr nonlinearity in optical fibers, the plasma nonlinearity in the channel can be utilized for pulse compression. The spectrum of laser pulses with an initial duration 10/sup 18/ W/cm/sup 2/).

A method for attosecond pulse measurement

Summary form only given. There exist a number of proposals for the generation of attosecond pulse trains or single attosecond pulses. Unfortunately, measurement of the duration of these pulses has not been possible to date. Currently used techniques are either limited by the pulse duration of the laser pulse, as in multiphoton cross correlation measurements, or by insufficient cross section, as in two photon absorption measurements. We present a novel technique for the measurement of attosecond pulses based on cross correlation between a strong laser pulse and an attosecond pulse in a noble gas. The method fundamentally differs from previously performed multiphoton cross correlation measurements, the resolution of which is limited by the laser pulse duration. In contrast, the resolution limit of our method lies at about one tenth of the optical period of the laser pulse. We investigate the method by numerically solving the 3-dimensional Schrodinger equation for a He/sup +/ ion.

Nonadiabatic self-phase-matching of keV high harmonic generation,

The nonadiabatic self modulation experienced by a few-cycle optical pulse propagating in a tunnel-ionizing gas can result in phase-matched high harmonic generation. Our calculations predict that the mechanism, which has been termed nonadiabatic self phase-matching, could make the generation of above keV x-ray harmonics possible for the first time.

Propagation effects in strong field atomic physics

Tunnel ionization is the primary process in matter exposed to high-intensity laser radiation and is relevant to a number of intriguing phenomena such as high harmonic generation, x-ray lasing, plasma heating, spectral blue shifting of laser pulses and particle acceleration.