Search results for "high harmonic generation"
showing 10 items of 66 documents
Observation of two-XUV-photon ionization using harmonic generation from a short, intense laser pulse
1996
We report the observation of a two-photon ionization process in the XUV wavelength regime. In a near-resonant 1 + 1 ionization scheme, Ar atoms are ionized absorbing the 15 eV third harmonic photons produced in a gas jet by the 0.5 ps intense laser pulses of a KrF excimer laser emitting at 248.6 nm. The present demonstration of a non-linear process in the XUV regime reveals feasibility of high-intensity applications utilizing the uniquely high peak power of non-conventional short wavelength radiation sources based on harmonic generation.
Harmonic Generation and Nonlinear Propagation: When Secondary Radiations Have Primary Consequences
2014
In this Letter, it is experimentally and theoretically shown that weak odd harmonics generated during the propagation of an infrared ultrashort ultraintense pulse unexpectedly modify the nonlinear properties of the medium and lead to a strong modification of the propagation dynamics. This result is in contrast with all current state-of-the-art propagation model predictions, in which secondary radiations, such as third harmonic, are expected to have a negligible action upon the fundamental pulse propagation. By analyzing full three-dimensional ab initio quantum calculations describing the microscopic atomic optical response, we have identified a fundamental mechanism resulting from interfere…
Symmetries in harmonic generation by a two-color field: an application to a simple model atom
1999
We show that the parity of the order of the harmonics generated by a bichromatic field with commensurate frequencies may be related to the invariance properties of the time-dependent Hamiltonian with respect to some suitable transformations. To simplify the mathematical treatment, we have used a simple model atom to perform calculations that show the effects of the relative phase of the driving fields. Harmonic generation has been described as a two-step process that involves replicas of the Stark levels. In agreement with other previous treatments in which other model atoms were used, we have found that a small contamination of the fundamental harmonic can produce significant modifications…
Laser even harmonics generation by a plasma embedded in a static electric field
2004
Even order harmonics generation of the laser radiation due to electron-ion collisions in a plasma embedded in a constant electric field is investigated theoretically. Even harmonics are generated because the presence of a static electric field removes the invariance of the electron distribution function under the symmetry operation of velocity direction inversion. Efficiency generation dependencies are investigatedvsdifferent significant parameters as: harmonics number; the ratio of the electron quiver velocity to the thermal velocity; the orientation of the constant electric field with respect to the laser radiation electric field and its wavevector. It is shown that in the general case th…
The Study Of The Nuclear Motion In D2+ Molecular Ion By Using The Harmonic Spectra
2007
In this paper we show how it is possible to investigate the nuclei dynamics of a D2+ molecular ion by using the high harmonic generation spectra emitted by the system when subjected to an intense laser field. In particular, the emitted spectra contains, in addition to the usual odd harmonic peaks, additional satellite peaks whose frequency spacing is equal to the vibrational frequency of the nuclei.
Nuclear Molecular Dynamics Investigated by Using High Order Harmonic Generation Spectra
2009
In this paper we show how it is possible to investigate the nuclear dynamics of simple molecular ions and molecules by looking at the high-order harmonic generation spectra they emit in the presence of a laser field. In particular we investigate two different effects: the presence of sidebands in the emitted spectra around the usual odd harmonics and an isotopic effect which affects the height of the plateau lines. We further study the advantages and the limitations of the semiclassical approach.
Laser driven structured quantum rings
2015
In this work we study harmonic emission from structured quantum rings (SQRs). In SQRs, electrons trapped in two-dimensional structures are further confined by an external potential composed of N scattering centers arranged on a circle. We build a suitable one-dimensional model Hamiltonian describing this class of systems and analytically solve the associated Schödinger equation. We find that the solution can be expressed in terms of Mathieu functions and focus on the specific case of N = 6. By exactly solving the time-dependent Schödinger equation, we then show how the harmonic response to linearly polarized lasers strongly depends on the ring physical parameters. The results illustrate how…
Evidence of Nuclear Motion in H2-like Molecule by Means of High Order Harmonic Generation
2008
The dynamics of hydrogen-like molecules is investigated beyond the usual fixed nuclei approximation. The nuclear motion introduces in the familiar spectrum of emitted radiation additional regular lines whose separation is essentially given by the vibrational frequency of nuclear motion. A wavelet analysis of the emitted spectrum shows that the intensity of the harmonic lines is modulated with the same period of the nuclear motion; this suggests the possibility of the real-time control of the nuclear dynamics.
Infrared radiation harmonic generation in degenerate semiconductors
2004
The basic properties of infrared laser radiation odd harmonic generation due to electron-charged impurity collisions in degenerate semiconductors are investigated. It is found that in the case of relatively weak fields, the electron Fermi distribution is the cause of an anomalous suppression of harmonic radiation. In the case of strong fields, the effect of the selective suppression of single harmonics is established.
Optical Harmonic Generation Parametric Devices
1999
The sections in this article are 1 Nonlinear Optics: an Actual and Wide Field Of Optics Research 2 Main Applications of Parametric Devices 3 Induced Macroscopic Polarization 4 Electromagnetic Energy Exchange 5 Nonlinear Materials 6 Propagation of the Waves in the Nonlinear Medium 7 Second Harmonic Generation 8 Optical Parametric Generators and Amplifiers 9 Optical Parametric Oscillators 10 Recent Advances in Frequency Conversion