reading.bib
@ARTICLE{Kalosha03,
AUTHOR = {Kalosha, V. P. and Herrmann, J.},
JOURNAL = {Physical Review A},
PAGES = {023812},
TITLE = {Ultrawide spectral broadening and compression of
single extremely short pulses in the visible, uv-vuv, and middle
infrared by high-order stimulated Raman scattering},
VOLUME = {68},
YEAR = {2003},
ABSTRACT = {We present the results of a comprehensive analytical
and numerical study of ultrawide spectral broadening and
compression of isolated extremely short visible, uv-vuv and middle
infrared (MIR) pulses by high-order stimulated Raman scattering in
hollow waveguides. Spectral and temporal characteristics of the
output pulses and the mechanism of pulse compression using
dispersion of the gas filling and output glass window are
investigated without the slowly varying envelope approximation.
Physical limitations due to phase mismatch, velocity walk off, and
pump-pulse depletion as well as improvements through the use of
pump-pulse sequences and dispersion control are studied. It is
shown that phase-locked pulses as short as similar to2 fs in the
visible and uv-vuv, and 6.5 fs in the MIR can be generated by
coherent scattering in impulsively excited Raman media without the
necessity of external phase control. Using pump-pulse sequences,
shortest durations in the range of about 1 fs for visible and
uv-vuv probe pulses are predicted.},
URL = {file:///T:/CDL-group/Tong/ref/PRA68_023812.pdf}
}
@ARTICLE{Dinu03,
AUTHOR = {Dinu, L. C. and Muller, H. G. and Kazamias, S. and
Mullot, G. and Auge, F. and Balcou, P. and Paul, P. M. and Kovacev,
M. and Breger, P. and Agostini, P.},
JOURNAL = {Physical Review Letters},
PAGES = {063901},
TITLE = {Measurement of the subcycle timing of attosecond XUV
bursts in high-harmonic generation},
VOLUME = {91},
YEAR = {2003},
ABSTRACT = {The absolute timing of the high-harmonic attosecond
pulse train with respect to the generating IR pump cycle has been
measured for the first time. The attosecond pulses occur 190+/-20
as after each pump field maxima (twice per optical cycle), in
agreement with the "short" quantum path of the quasiclassical model
of harmonic generation.},
URL = {file:///T:/CDL-group/Tong/ref/prl91_063901.pdf}
}
@ARTICLE{Papadogiannis03,
AUTHOR = {Papadogiannis, N. A. and Nikolopoulos, L. A. A. and
Charalambidis, D. and Tsakiris, G. D. and Tzallas, P. and Witte,
K.},
JOURNAL = {Applied Physics B-Lasers And Optics},
PAGES = {721-727},
TITLE = {On the feasibility of performing non-linear
autocorrelation with attosecond pulse trains},
VOLUME = {76},
YEAR = {2003},
ABSTRACT = {We present experimental results in which a
second-order effect, namely two-photon ionization of atomic He
induced by a superposition of harmonics, is observed. The harmonics
are generated in a Xe gas-jet using a 790-nm 10-Hz femtosecond
Ti:sapphire laser and are subsequently focused into a He gas-jet
with a Kirkpatrick-Baez arrangement. The superposition is formed by
using a thin In filter and it comprises the 7th to 13th harmonics.
Solving the time-dependent Schrodinger equation for He in a
polychromatic laser field, the He+ ion yield is calculated as a
function of the total XUV intensity. Using the calculated yield and
taking into account the focusing and transmission properties of the
arrangement, the number of He+ ions produced per laser pulse is
estimated and is found to be in reasonable agreement with its
measured value. The total number of ions produced non-resonantly
follows a nearly quadratic dependence on the harmonic intensity,
thus establishing the feasibility of a second-order
auto-correlation measurement of the superposition of harmonics,
i.e., of a direct temporal characterization of attosecond pulse
trains.}
}
@ARTICLE{Kitzler03,
AUTHOR = {Kitzler, M. and Fabian, C. and Milosevic, N. and
Scrinzi, A. and Brabec, T.},
JOURNAL = {Journal Of The Optical Society Of America B-Optical
Physics},
PAGES = {591-596},
TITLE = {Quantum theory of single subfemtosecond
extreme-ultraviolet pulse measurements},
VOLUME = {20},
YEAR = {2003},
ABSTRACT = {Recently the initial measurements of single attosecond
pulses with laser-dressed single-photon XUV ionization of gas atoms
were reported. Determination of the extreme-ultraviolet (XUV) pulse
duration from the electron spectrum is based on a classical theory.
Although classical models are known to give a qualitatively correct
description of strong laser-atom interaction, the validity range
for accurate determination of subfemtosecond pulses must be
scrutinized by quantum mechanical analysis. We establish a
theoretical framework for the accurate temporal characterization of
attosecond XUV pulses by using a Fourier-Bessel expansion of the
XUV electron spectrum under the strong field approximation and a
semiclassical derivation, setting earlier results on a rigorous
theoretical footing. Our analysis reveals an improved scheme that
is by more than an order of magnitude more efficient than the one
used so far and allows for direct experimental discrimination
between single and multiple attosecond pulses. (C) 2003 Optical
Society of America.}
}
@ARTICLE{Kitzler02,
AUTHOR = {Kitzler, M. and Milosevic, N. and Scrinzi, A. and
Krausz, F. and Brabec, T.},
JOURNAL = {Physical Review Letters},
PAGES = {173904},
TITLE = {Quantum theory of attosecond XUV pulse measurement by
laser dressed photoionization},
VOLUME = {88},
YEAR = {2002},
ABSTRACT = {The first reported measurements of single attosecond
pulses use laser dressed single-photon extreme ultraviolet (XUV)
ionization of gas atoms. The determination of XUV pulse duration
from the electron spectrum is based on a classical theory. Although
classical models are known to give a qualitatively correct
description of strong laser atom interaction, the validity must be
scrutinized by a quantum-mechanical analysis. We establish a
theoretical framework for the accurate temporal characterization of
attosecond XUV pulses. Our analysis reveals an improved scheme that
allows for direct experimental discrimination between single and
multiple attosecond pulses.}
}
@ARTICLE{Quere03,
AUTHOR = {Quere, F. and Itatani, J. and Yudin, G. L. and Corkum,
P. B.},
JOURNAL = {Physical Review Letters},
PAGES = {073902},
TITLE = {Attosecond spectral shearing interferometry},
VOLUME = {90},
YEAR = {2003},
ABSTRACT = {We show that the complete characterization of
arbitrarily short isolated attosecond x-ray pulses can be achieved
by applying spectral shearing interferometry to photoelectron wave
packets. These wave packets are coherently produced through the
photoionization of atoms by two time-delayed replicas of the x-ray
pulse, and are shifted in energy with respect to each other by
simultaneously applying a strong laser field. The x-ray pulse is
reconstructed with the algorithm developed for optical pulses,
which requires no knowledge of ionization physics. Using a 800-nm
shearing field, x-ray pulses shorter than similar to400 asec can be
fully characterized.}
}
@ARTICLE{Zeng03,
AUTHOR = {Zeng, Z. N. and Li, R. X. and Yu, W. and Xu, Z. Z.},
JOURNAL = {Physical Review A},
PAGES = {013815},
TITLE = {Effect of the carrier-envelope phase of the driving
laser field on the high-order harmonic attosecond pulse},
VOLUME = {67},
YEAR = {2003},
ABSTRACT = {The effect of the carrier-envelope phase of a
few-cycle driving laser field on the generation and measurement of
high-order harmonic attosecond pulses is investigated
theoretically. We find that the position of the generated
attosecond soft-x-ray pulse in the cutoff region is locked to the
oscillation of the driving laser field, but not to the envelope of
the laser pulse. This property ensures the success of the width
measurement of an attosecond soft-x-ray pulse based on the cross
correlation between the attosecond pulse and its driving laser
pulse [M. Hentschel , Nature (London) 414, 509 (2001)]. However,
there still exists a timing jitter of the order of tens of
attoseconds between the attosecond pulse and its driving laser
field. We also propose a method to detect the carrier-envelope
phase of the driving laser field by measuring the spatial
distribution of the photoelectrons induced by the attosecond
soft-x-ray pulse and its driving laser pulse.}
}
@ARTICLE{Niikura03,
AUTHOR = {Niikura, H. and Legare, F. and Hasbani, R. and Ivanov,
M. Y. and Villeneuve, D. M. and Corkum, P. B.},
JOURNAL = {Nature},
PAGES = {826-829},
TITLE = {Probing molecular dynamics with attosecond resolution
using correlated wave packet pairs},
VOLUME = {421},
YEAR = {2003},
ABSTRACT = {Spectroscopic measurements with increasingly higher
time resolution are generally thought to require increasingly
shorter laser pulses, as illustrated by the recent monitoring of
the decay of core-excited krypton(1) using attosecond photon
pulses(2),(3). However, an alternative approach to probing
ultrafast dynamic processes might be provided by entanglement,
which has improved the precision(4,5) of quantum optical
measurements. Here we use this approach to observe the motion of a
D-2(+) vibrational wave packet formed during the multiphoton
ionization of D-2 over several femtoseconds with a precision of
about 200 attoseconds and 0.05 angstroms, by exploiting the
correlation between the electronic and nuclear wave packets formed
during the ionization event. An intense infrared laser field drives
the electron wave packet, and electron recollision(6-11) probes the
nuclear motion. Our results show that laser pulse duration need not
limit the time resolution of a spectroscopic measurement, provided
the process studied involves the formation of correlated wave
packets, one of which can be controlled; spatial resolution is
likewise not limited to the focal spot size or laser wavelength.}
}
@ARTICLE{Niikura02,
AUTHOR = {Niikura, H. and Legare, F. and Hasbani, R. and
Bandrauk, A. D. and Ivanov, M. Y. and Villeneuve, D. M. and Corkum,
P. B.},
JOURNAL = {Nature},
PAGES = {917-922},
TITLE = {Sub-laser-cycle electron pulses for probing molecular
dynamics},
VOLUME = {417},
YEAR = {2002},
ABSTRACT = {Experience shows that the ability to make measurements
in any new time regime opens new areas of science. Currently,
experimental probes for the attosecond time regime (10(-18)-10(-15)
s) are being established. The leading approach is the generation of
attosecond optical pulses by ionizing atoms with intense laser
pulses. This nonlinear process leads to the production of high
harmonics during collisions between electrons and the ionized
atoms. The underlying mechanism implies control of energetic
electrons with attosecond precision. We propose that the electrons
themselves can be exploited for ultrafast measurements. We use a
'molecular clock', based on a vibrational wave packet in H-2(+) to
show that distinct bunches of electrons appear during electron-ion
collisions with high current densities, and durations of about 1
femtosecond (10(-15) s). Furthermore, we use the molecular clock to
study the dynamics of non-sequential double ionization.}
}
@ARTICLE{Bandrauk02,
AUTHOR = {Bandrauk, A. D. and Chelkowski, S. and Shon, N. H.},
JOURNAL = {Physical Review Letters},
PAGES = {283903},
TITLE = {Measuring the electric field of few-cycle laser pulses
by attosecond cross correlation},
VOLUME = {89},
YEAR = {2002},
ABSTRACT = {A new technique for directly measuring the electric
field of linearly polarized few-cycle laser pulses is proposed.
Based on the solution of the time-dependent Schrodinger equation
(TDSE) for an H atom in the combined field of infrared (IR)
femtosecond (fs) and ultraviolet (UV) attosecond (as) laser pulses
we show that, as a function of the time delay between two pulses,
the difference (or equivalently, asymmetry) of photoelectron
signals in opposite directions (along the polarization vector of
laser pulses) reproduces very well the profile of the electric
field (or vector potential) in the IR pulse. Such ionization
asymmetry can be used for directly measuring the carrier-envelope
phase difference (i.e., the relative phase of the carrier frequency
with respect to the pulse envelope) of the IR fs laser pulse.}
}
@ARTICLE{Nakajima02,
AUTHOR = {Nakajima, T. and Nikolopoulos, L. A. A.},
JOURNAL = {Physical Review A},
PAGES = {041402},
TITLE = {Use of helium double ionization for autocorrelation of
an xuv pulse},
VOLUME = {66},
YEAR = {2002},
ABSTRACT = {We investigate a simple scheme for autocorrelation
measurement of an xuv pulse. It is based on double ionization of
He. We have found that, in a certain photon energy range, the
detection of doubly charged positive ions instead of
energy-resolved photoelectrons is sufficient for autocorrelation,
which greatly simplifies the detection system for practical use.}
}
@ARTICLE{GaardeS02,
AUTHOR = {Gaarde, M. B. and Schafer, K. J.},
JOURNAL = {Physical Review Letters},
PAGES = {213901},
TITLE = {Space-time considerations in the phase locking of high
harmonics},
VOLUME = {89},
YEAR = {2002},
ABSTRACT = {The combination of several high order harmonics can
produce an attosecond pulse train, provided that the harmonics are
locked in phase to each other. We present calculations that
evaluate the degree of phase locking that is achieved in argon and
neon gases interacting with an intense, 50 fs laser pulse, for a
range of macroscopic conditions. We find that phase locking depends
on both the temporal and the spatial phase behavior of the
harmonics, as determined by the interplay between the intrinsic
dipole phase and the phase matching in the nonlinear medium. We
show that, as a consequence of this, it is not possible to
compensate for a lack of phase locking by purely temporal phase
manipulation.}
}
@ARTICLE{Gavrila02,
AUTHOR = {Gavrila, M.},
JOURNAL = {Journal Of Physics B-Atomic Moleculbp And Optical
Physics},
PAGES = {R147-R193},
TITLE = {Atomic stabilization in superintense laser fields},
VOLUME = {35},
YEAR = {2002},
ABSTRACT = {Atomic stabilization is a highlight of superintense
laser-atom physics. A wealth of information has been gathered on
it; established physical concepts have been revised in the process;
points of contention have been debated. Recent technological
breakthroughs are opening exciting perspectives of experimental
study. With this in mind, we present a comprehensive overview of
the phenomenon.We discuss the two forms of atomic stabilization
identified theoretically. The first one, 'quasistationary
(adiabatic) stabilization' (QS), refers to the limiting case of
plane-wave monochromatic radiation. QS characterizes the fact that
ionization rates, as calculated from single-state Floquet theory,
decrease with intensity (possibly in an oscillatory manner) at high
values of the field. We present predictions for QS from various
forms of Floquet theory: high frequency (that has led to its
discovery and offers the best physical insight), complex scaling,
Sturmian, radiative close coupling and R-matrix. These predictions
all agree quantitatively, and high-accuracy numerical results have
been obtained for hydrogen. Predictions from non-Floquet theories
are also discussed. Thereafter, we analyse the physical origin of
QS.The alternative form of stabilization, 'dynamic stabilization'
(DS), is presented next. Ibis expresses the fact that the
ionization probability at the end of a laser pulse of fixed shape
and duration does not approach unity as the peak intensity is
increased, but either starts decreasing with the intensity
(possibly in an oscillatory manner), or flattens out at a value
smaller than unity. We review the extensive research done on
one-dimensional models, that has provided valuable insights into
the phenomenon; twoand three-dimensional models are also
considered. Full three-dimensional Coulomb calculations have
encountered severe numerical handicaps in the past, and it is only
recently that a comprehensive mapping of DS could be made for
hydrogen. An adiabatic variation of the laser-pulse envelope keeps
the system in the Floquet state associated with the initial state,
that allows calculation of the ionization probability in terms of
the corresponding rate. A nonadiabatic variation can excite other
Floquet states, either discrete ('shake-up') or continuous
('shake-off'), with considerable consequences for DS. A unitary
interpretation of these aspects of DS is presented in terms of
'multistate Floquet theory'. We then comment on the points of
contention raised in connection with DS. Further, we review the
extent to which the classical approach has been successful in
describing DS.We next examine the concern that nonrelativistic (NR)
predictions for stabilization may be inadequate in superintense
fields, because relativistic corrections would invalidate them. It
turns out that, although the relativistic corrections do limit
stabilization, there is an ample 'window' of intensities for which
the NR predictions remain valid.Finally, we discuss the
experimental evidence in favour of stabilization. For lack of
adequate lasers to study ground states of single-active-electron
atoms, the experiments so far have been performed on low-lying
Rydberg states. Two state-of-the-art experiments have determined
ionization yields for pulses with adiabatic envelopes. Their
results concur, are in agreement with the theoretical predictions
and represent a clear-cut confirmation of DS.Our conclusion is that
superintense field stabilization is firmly established, both
theoretically and experimentally. Nevertheless, further research is
desirable to solve interesting open problems, some of which we
identify. Their research is made timely by the superintense
high-frequency light sources that are being developed, such as
VUV-FELs, or attosecond pulses from high-harmonic generation.}
}
@ARTICLE{Drescher02,
AUTHOR = {Drescher, M. and Hentschel, M. and Kienberger, R. and
Uiberacker, M. and Yakovlev, V. and Scrinizi, A. and
Westerwalbesloh, T. and Kleineberg, U. and Heinzmann, U. and
Krausz, F.},
JOURNAL = {Nature},
PAGES = {803-807},
TITLE = {Time-resolved atomic inner-shell spectroscopy},
VOLUME = {419},
YEAR = {2002},
ABSTRACT = {The characteristic time constants of the relaxation
dynamics of core-excited atoms have hitherto been inferred from the
linewidths of electronic transitions measured by continuous-wave
extreme ultraviolet or X-ray spectroscopy. Here we demonstrate that
a laser-based sampling system, consisting of a few-femtosecond
visible light pulse and a synchronized sub-femtosecond soft X-ray
pulse, allows us to trace these dynamics directly in the time
domain with attosecond resolution. We have measured a lifetime of
7.9(-0.9)(+1.0) fs of M-shell vacancies of krypton in such a
pump-probe experiment.}
}
@ARTICLE{Drescher01,
AUTHOR = {Drescher, M. and Hentschel, M. and Kienberger, R. and
Tempea, G. and Spielmann, C. and Reider, G. A. and Corkum, P. B.
and Krausz, F.},
JOURNAL = {Science},
PAGES = {1923-1927},
TITLE = {X-ray pulses approaching the attosecond frontier},
VOLUME = {291},
YEAR = {2001},
ABSTRACT = {Single soft-x-ray pulses of similar to 90-electron
volt (eV) photon energy are produced by high-order harmonic
generation with 7-femtosecond (fs), 770-nanometer (1.6 eV) Laser
pulses and are characterized by photoionizing krypton in the
presence of the driver laser pulse. By detecting photoelectrons
ejected perpendicularly to the Laser polarization, broadening of
the photoelectron spectrum due to absorption and emission of Laser
photons is suppressed, permitting the observation of a
Laser-induced downshift of the energy spectrum with sub-laser-cycle
resolution in a cross correlation measurement. We measure isolated
x-ray pulses of 1.8 (+0.7/-1.2) fs in duration, which are shorter
than the oscillation cycle of the driving Laser Light (2.6 fs). Our
techniques for generation and measurement offer sub-femtosecond
resolution over a wide range of x-ray wavelengths, paving the way
to experimental attosecond science. Tracing atomic processes
evolving faster than the exciting light field is within reach.}
}
@ARTICLE{Kienberger02,
AUTHOR = {Kienberger, R. and Hentschel, M. and Uiberacker, M.
and Spielmann, C. and Kitzler, M. and Scrinzi, A. and Wieland, M.
and Westerwalbesloh, T. and Kleineberg, U. and Heinzmann, U. and
Drescher, M. and Krausz, F.},
JOURNAL = {Science},
PAGES = {1144-1148},
TITLE = {Steering attosecond electron wave packets with light},
VOLUME = {297},
YEAR = {2002},
ABSTRACT = {Photoelectrons excited by extreme ultraviolet or x-ray
photons in the presence of a strong laser field generally suffer a
spread of their energies due to the absorption and emission of
laser photons. We demonstrate that if the emitted electron wave
packet is temporally confined to a small fraction of the
oscillation period of the interacting light wave, its energy
spectrum can be upor down-shifted by many times the laser photon
energy without substantial broadening. The light wave can
accelerate or decelerate the electrons drift velocity, i.e., steer
the electron wave packet like a classical particle. This capability
strictly relies on a sub-femtosecond duration of the ionizing x-ray
pulse and on its timing to the phase of the light wave with a
similar accuracy, offering a simple and potentially single-shot
diagnostic tool for attosecond pump-probe spectroscopy.}
}
@ARTICLE{Kienberger02,
AUTHOR = {Kienberger, R. and Hentschel, M. and Spielmann, C. and
Reider, G. A. and Milosevic, N. and Heinzmann, U. and Drescher, M.
and Krausz, F.},
JOURNAL = {Applied Physics B-Lasers And Optics},
PAGES = {S3-S9},
TITLE = {Sub-femtosecond X-ray pulse generation and
measurement},
VOLUME = {74},
YEAR = {2002},
ABSTRACT = {We report the generation and measurement of isolated
soft-X-ray pulses (lambda(X) = 14 nm) with a duration of tau(X) =
650 150 attoseconds (as) by using few-cycle intense
visible/near-infrared (lambda(0) = 750 nm) laser pulses. For the
temporal characterization of the X-ray pulses, a cross-correlation
technique relying on laser field assisted X-ray photoemission from
krypton atoms was employed. The experimental results bear direct
evidence of the X-ray pulse being synchronized to the field
oscillations of the visible-light pulse with attosecond precision
and of bound-free electronic transitions from the 4p state of
krypton responding to 90-eV excitation on an attosecond time scale.
As a first demonstration of attosecond metrology, the synchronized
single sub-fs X-ray pulses were used for tracing the electric field
oscillations in a visible-light wave with a resolution of better
than 150 as.}
}
@ARTICLE{Muller02,
AUTHOR = {Muller, H. G.},
JOURNAL = {Applied Physics B-Lasers And Optics},
PAGES = {S17-S21},
TITLE = {Reconstruction of attosecond harmonic beating by
interference of two-photon transitions},
VOLUME = {74},
YEAR = {2002},
ABSTRACT = {A method is proposed for detailed determination of the
temporal structure of XUV pulses. The method is especially suited
for diagnostics on attosecond pulses and pulse trains that
originate from temporal beating of various harmonics of an
ultrashort laser pulse. A recent experiment already showed the
feasibility of this method when applied to long attosecond pulse
trains, where it measured the average pulse characteristics. Here
we argue that the same method is also suitable for determining
differences between the individual attosecond pulses in a short
train, or the properties of a single attosecond pulse.}
}
@ARTICLE{Nicolaides02,
AUTHOR = {Nicolaides, C. A. and Mercouris, T. and Komninos, Y.},
JOURNAL = {Journal Of Physics B-Atomic Moleculbp And Optical
Physics},
PAGES = {L271-L279},
TITLE = {Attosecond dynamics of electron correlation in doubly
excited atomic states},
VOLUME = {35},
YEAR = {2002},
ABSTRACT = {We have solved the time-dependent Schrodinger equation
describing the simultaneous interaction of the He 1s2s S-1 state
with two laser-generated pulses of trapezoidal or Gaussian shape,
of duration 86 fs and of frequencies omega(1) = 1.453 au and
omega(2) = 1.781 au. The system is excited to the energy region of
two strongly correlated doubly excited states, chosen for this
study according to specific criteria. It is demonstrated
quantitatively that, provided one focuses on the dynamics occurring
within the attosecond timescale, the corresponding orbital
configurations, 2s2p and 2p3d P-1(o), exist as nonstationary
states, with occupation probabilities that are oscillating as the
states decay exponentially into the 1sepsilonp continuum, during
and after the laser-atom interaction. It follows that it is
feasible to probe by attosecond pulses the motion of configurations
of electrons as they correlate via the total Hamiltonian. For the
particular system studied here, the probe pulses could register the
oscillating doubly excited configurations by de-exciting to the He
1s3d D-1 state, which emits at 6680 Angstrom.}
}
@ARTICLE{Itatani02,
AUTHOR = {Itatani, J. and Quere, F. and Yudin, G. L. and Ivanov,
M. Y. and Krausz, F. and Corkum, P. B.},
JOURNAL = {Physical Review Letters},
PAGES = {173903},
TITLE = {Attosecond streak camera},
VOLUME = {88},
YEAR = {2002},
ABSTRACT = {An electron generated by x-ray photoionization can be
deflected by a strong laser field. Its energy and angular
distribution depends on the phase of the laser field at the time of
ionization. This phase dependence can be used to measure the
duration and chirp of single sub100-attosecond x-ray pulses.}
}
@ARTICLE{Milosevic00,
AUTHOR = {Milosevic, D. B. and Becker, W.},
JOURNAL = {Physical Review A},
PAGES = {011403},
TITLE = {Attosecond pulse trains with unusual nonlinear
polarization},
VOLUME = {6201},
YEAR = {2000},
ABSTRACT = {The phases of the circularly polarized harmonics with
alternating helicity generated by a bichromatic laser field whose
two components are circularly polarized in the same plane but
rotate in opposite directions an investigated. Only one trajectory
contributes to harmonic generation in the plateau region. The
dependence of the harmonic phase on the laser field intensity is
weak (with the slope similar to 0.2 U-p /omega). Adjacent harmonics
having the same helicity are relatively closely phase locked. As a
result, a train of three attosecond pulses per optical cycle of the
driving field is generated, each having a width of 80 as. Depending
upon whether the two helicity components can be separated the
polarization of the pulses is close to circular or close to linear
with three different orientations per optical cycle.}
}
@ARTICLE{Milosevic02,
AUTHOR = {Milosevic, N. and Scrinzi, A. and Brabec, T.},
JOURNAL = {Physical Review Letters},
PAGES = {093905},
TITLE = {Numerical characterization of high harmonic attosecond
pulses},
VOLUME = {88},
YEAR = {2002},
ABSTRACT = {A numerical simulation of attosecond harmonic pulse
generation in a three-dimensional field-ionizing gas is presented.
Calculated harmonic efficiencies quantitatively reproduce
experimental findings. This allows a quantitative characterization
of attosecond pulse generation revealing information currently not
accessible by experiment. The rapid phase variation and
spatiotemporal distortions of harmonics are smaller than
anticipated, allowing focusing of 30-nm, 750-as pulses to
intensities in excess of 10(13) W/cm(2). Feasibility of such pulses
brings novel applications such as extreme ultraviolet nonlinear
optics and attosecond pump probe spectroscopy within reach.}
}
@ARTICLE{Hentschel01,
AUTHOR = {Hentschel, M. and Kienberger, R. and Spielmann, C. and
Reider, G. A. and Milosevic, N. and Brabec, T. and Corkum, P. and
Heinzmann, U. and Drescher, M. and Krausz, F.},
JOURNAL = {Nature},
PAGES = {509-513},
TITLE = {Attosecond metrology},
VOLUME = {414},
YEAR = {2001},
ABSTRACT = {The generation of ultrashort pulses is a key to
exploring the dynamic behaviour of matter on ever-shorter
timescales. Recent developments have pushed the duration of laser
pulses close to its natural limit-the wave cycle, which lasts
somewhat longer than one femtosecond (1 fs = 10(-15) s) in the
visible spectral range. Time-resolved measurements with these
pulses are able to trace dynamics of molecular structure, but fail
to capture electronic processes occurring on an attosecond (1 as =
10(-18) s) timescale. Here we trace electronic dynamics with a time
resolution of less than or equal to 150 as by using a
subfemtosecond soft-X-ray pulse and a few-cycle visible light
pulse. Our measurement indicates an attosecond response of the
atomic system, a soft-X-ray pulse duration of 650 +/- 150 as and an
attosecond synchronism of the soft-X-ray pulse with the light
field. The demonstrated experimental tools and techniques open the
door to attosecond spectroscopy of bound electrons.}
}
@ARTICLE{Christov01,
AUTHOR = {Christov, I. P. and Bartels, R. and Kapteyn, H. C. and
Murnane, M. M.},
JOURNAL = {Physical Review Letters},
PAGES = {5458-5461},
TITLE = {Attosecond time-scale intra-atomic phase matching of
high harmonic generation},
VOLUME = {86},
YEAR = {2001},
ABSTRACT = {Using a model of high-harmonic generation that couples
a fully quantum calculation with a semiclassical electron
trajectory picture, we show that a new type of phase matching is
possible when an atom is driven by an optimal optical waveform. For
an optimized laser pulse shape, strong constructive interference is
obtained in the frequency domain between emissions from different
electron trajectories, thereby selectively enhancing a particular
harmonic order. This work demonstrates that coherent control in the
strong-held regime is possible by adjusting the peaks or a laser
field on an attosecond time scale.}
}
@ARTICLE{Shon01,
AUTHOR = {Shon, N. H. and Suda, A. and Tamaki, Y. and
Midorikawa, K.},
JOURNAL = {Physical Review A},
PAGES = {063806},
TITLE = {High-order harmonic and attosecond pulse generations:
Bulk media versus hollow waveguides},
VOLUME = {6306},
YEAR = {2001},
ABSTRACT = {Generation and propagation of high-order harmonics by
intense, ultrashort laser pulses in static gas cells and gas-filled
hollow waveguides are numerically investigated. The calculations
are performed utilizing a self-consistent solution of the
time-dependent Schrodinger and wave equations. It is shown that,
when the 30-fs laser pulse is focused into a gas cell the emission
spectrum consists of discrete and well-resolved harmonics. These
high-order harmonics can be used for generation of a train of
subfemtosecond pulses. When the 5-fs laser pulse propagates along a
gas-filled hollow waveguide the emission spectrum exhibits a
quasicontinous structure that permits the generation of a single
subfemtosecond pulse. The effects of laser intensity and position
of the interacting medium relative to the laser focus on the
emission spectrum and pulse profile are investigated. The
differences between results obtained by our model and by the model
that uses the strong-field approximation for single-atom
calculations are discussed.}
}
@ARTICLE{Apolonski00,
AUTHOR = {Apolonski, A. and Poppe, A. and Tempea, G. and
Spielmann, C. and Udem, T. and Holzwarth, R. and Hansch, T. W. and
Krausz, E.},
JOURNAL = {Physical Review Letters},
PAGES = {740-743},
TITLE = {Controlling the phase evolution of few-cycle light
pulses},
VOLUME = {85},
YEAR = {2000},
ABSTRACT = {Using a coherent nonlinear optical technique, slipping
of the carrier through the envelope of 6-fs light wave packets
emitted from a mode-locked-oscillator/pulse-compressor system has
been measured, permitting the generation of intense, few-cycle
light with precisely reproducible electric and magnetic fields.
These pulses open the way to controlling the evolution of
strong-field interactions on the time scale of the light
oscillation cycle and are indispensable to reproducible attosecond
x-ray pulse generation.}
}
This file has been generated by
bibtex2html 1.63