N. Dudovich - Academia.edu (original) (raw)

Papers by N. Dudovich

Physical Review A, 2002

Using femtosecond pulse-shaping techniques, we are able to control several useful parameters of c... more Using femtosecond pulse-shaping techniques, we are able to control several useful parameters of coherent anti-Stokes Raman spectroscopy ͑CARS͒. By shaping both the pump and the Stokes pulses with an appropriate spectral phase function, we eliminated the nonresonant CARS background. In addition, we designed pulses which selectively excite one of two neighboring Raman levels, even when both are well within the excitation spectrum. High-resolution CARS spectra were recorded in spite of the broad femtosecond pulse spectrum.

Journal of Physics B: Atomic, Molecular and Optical Physics, 2014

High-harmonics generation spectroscopy is a promising tool for resolving electron dynamics and st... more High-harmonics generation spectroscopy is a promising tool for resolving electron dynamics and structure in atomic and molecular systems. This scheme, commonly described by the strong field approximation, requires a deep insight into the basic mechanism that leads to the harmonics generation. Recently, we have demonstrated the ability to resolve the first stage of the process -field induced tunnel ionization -by adding a weak perturbation to the strong fundamental field. Here we generalize this approach and show that the assumptions behind the strong field approximation are valid over a wide range of tunnel ionization conditions. Performing a systematic study -modifying the fundamental wavelength, intensity and atomic system -we observed a good agreement with quantum path analysis over a range of Keldysh parameters. The generality of this scheme opens new perspectives in high harmonics spectroscopy, holding the potential of probing large, complex molecular systems.

2006 IEEE LEOS Annual Meeting Conference Proceedings, 2006

In this paper attosecond measurement relies on a phase "gate&amp... more In this paper attosecond measurement relies on a phase "gate". The phase of attosecond pulses is easily manipulated because attosecond pulses arise in an interferometric process - the interferometer formed by an electron being removed by the atom, propagating in the laser field and re-colliding with the parent ion where the interference occurs. Slightly modifying (gating) the phase of the

19th International Conference on Ultrafast Phenomena, 2014

ABSTRACT We studied the two-color HHG emission from xenon in the giant resonance spectral region.... more ABSTRACT We studied the two-color HHG emission from xenon in the giant resonance spectral region. We found a substantial departure from the behavior expected for the single-active-electron picture which could be ascribed to electron correlation effects.

19th International Conference on Ultrafast Phenomena, 2014

ABSTRACT Extending the dimensionality of high harmonic generation (HHG) measurements has the pote... more ABSTRACT Extending the dimensionality of high harmonic generation (HHG) measurements has the potential to reconstruct structural features in molecules and resolve multielectron dynamics on attosecond time scales. We demonstrate that structural and dynamical effects in molecules can be unambiguously distinguished using multidimensional HHG techniques.

Strong field transient grating spectroscopy has shown to be a very versatile tool in time-resolve... more Strong field transient grating spectroscopy has shown to be a very versatile tool in time-resolved molecular spectroscopy. Here we use this technique to investigate the high-order harmonic generation from SF6 molecules vibrationally excited by impulsive stimulated Raman scattering. Transient grating spectroscopy enables us to reveal clear modulations of the harmonic emission. This heterodyne detection shows that the harmonic emission generated between 14 to 26 eV is mainly sensitive to two among the three active Raman modes in SF6, i.e. the strongest and fully symmetric υ1-A1g mode (774 cm −1 , 43 fs) and the slowest mode υ5-T2g (524 cm −1 , 63 fs). A time-frequency analysis of the harmonic emission reveals additional dynamics: the strength and central frequency of the υ1 mode oscillate with a frequency of 52 cm −1 (640 fs). This could be a signature of the vibration of dimers in the generating medium. Harmonic 11 shows a remarkable behavior, oscillating in opposite phase, both on the fast (774 cm −1 ) and slow (52 cm −1 ) timescales, which indicates a strong modulation of the recombination matrix element as a function of the nuclear geometry. These results demonstrate that the high sensitivity of high-order harmonic generation to molecular vibrations, associated to the high sensitivity of transient grating spectroscopy, make their combination a unique tool to probe vibrational dynamics.

Optics express, Jan 20, 2014

Phase measurement is a long-standing challenge in a wide range of applications, from X-ray imagin... more Phase measurement is a long-standing challenge in a wide range of applications, from X-ray imaging to astrophysics and spectroscopy. While in some scenarios the phase is resolved by an interferometric measurement, in others it is reconstructed via numerical optimization, based on some a-priori knowledge about the signal. The latter commonly use iterative algorithms, and thus have to deal with their convergence, stagnation, and robustness to noise. Here we combine these two approaches and present a new scheme, termed double blind Fourier holography, providing an efficient solution to the phase problem in two dimensions, by solving a system of linear equations. We present and experimentally demonstrate our approach for the case of lens-less imaging.

Uvx 2008: 9e Colloque Sur Les Sources Coherentes Et Incoherentes Uv, Vuv Et X; Applications Et Developpements Recents, 2008

ABSTRACT The high order harmonic generation process from molecules can be used to probe the struc... more ABSTRACT The high order harmonic generation process from molecules can be used to probe the structure of the emitting medium with high spatial resolution [1,2]. The measurements of molecular dynamics with such a probe is thus very appealing. Contrast is an important issue in pump probe spectroscopy: in general the probe only excites part of the molecules, so that the detected signal can be dominated by contributions from non-excited molecules. In this article we review two techniques that can be used to enhance the contrast of pump probe measurements: transient grating, spectroscopy and polarization-resolved spectroscopy. We use these techniques to detect rotational wavepackets and demonstrate a dramatic improvement in the contrast of the measured signal.

International Conference on Ultrafast Phenomena, 2010

ABSTRACT

Physical Review Letters, 2013

In strong-field light-matter interactions, the strong laser field dominates the dynamics. However... more In strong-field light-matter interactions, the strong laser field dominates the dynamics. However, recent experiments indicate that the Coulomb force can play an important role as well. In this Letter, we have studied the photoelectron momentum distributions produced from noble gases in elliptically polarized, 800 nm laser light. By performing a complete mapping of the three-dimensional electron momentum, we find that Coulomb focusing significantly narrows the lateral momentum spread. We find a surprisingly sensitive dependence of Coulomb focusing on the initial transverse momentum distribution, i.e., the momentum at the moment of birth of the photoelectron. We also observe a strong signature of the low-energy structure in the above threshold ionization spectrum.

Physical Review A, 2004

In spectroscopy, the fingerprint of a substance is usually comprised of a sequence of spectral li... more In spectroscopy, the fingerprint of a substance is usually comprised of a sequence of spectral lines with characteristic frequencies and strengths. Identification of substances often involves postprocessing, where the measured spectrum is compared with tabulated fingerprint spectra. Here we suggest a scheme for nonlinear spectroscopy, where, through coherent control of the nonlinear process, the information from the entire spectrum can

Nature Physics, 2006

Generating attosecond pulses has required a radically different approach from previous ultrafast ... more Generating attosecond pulses has required a radically different approach from previous ultrafast optical methods.

IEEE Journal of Quantum Electronics, 2001

Abstract—Under certain conditions, a high-finesse resonance phenomenon can occur in a grating wav... more Abstract—Under certain conditions, a high-finesse resonance phenomenon can occur in a grating waveguide structure (GWS). By varying these conditions, a shift in the resonance wavelength can be achieved. Specifically, utilizing the high finesse property of the GWS, small ...

Physical Review A, 2002

Using femtosecond pulse-shaping techniques, we are able to control several useful parameters of c... more Using femtosecond pulse-shaping techniques, we are able to control several useful parameters of coherent anti-Stokes Raman spectroscopy ͑CARS͒. By shaping both the pump and the Stokes pulses with an appropriate spectral phase function, we eliminated the nonresonant CARS background. In addition, we designed pulses which selectively excite one of two neighboring Raman levels, even when both are well within the excitation spectrum. High-resolution CARS spectra were recorded in spite of the broad femtosecond pulse spectrum.

Journal of Physics B: Atomic, Molecular and Optical Physics, 2014

High-harmonics generation spectroscopy is a promising tool for resolving electron dynamics and st... more High-harmonics generation spectroscopy is a promising tool for resolving electron dynamics and structure in atomic and molecular systems. This scheme, commonly described by the strong field approximation, requires a deep insight into the basic mechanism that leads to the harmonics generation. Recently, we have demonstrated the ability to resolve the first stage of the process -field induced tunnel ionization -by adding a weak perturbation to the strong fundamental field. Here we generalize this approach and show that the assumptions behind the strong field approximation are valid over a wide range of tunnel ionization conditions. Performing a systematic study -modifying the fundamental wavelength, intensity and atomic system -we observed a good agreement with quantum path analysis over a range of Keldysh parameters. The generality of this scheme opens new perspectives in high harmonics spectroscopy, holding the potential of probing large, complex molecular systems.

2006 IEEE LEOS Annual Meeting Conference Proceedings, 2006

In this paper attosecond measurement relies on a phase "gate&amp... more In this paper attosecond measurement relies on a phase "gate". The phase of attosecond pulses is easily manipulated because attosecond pulses arise in an interferometric process - the interferometer formed by an electron being removed by the atom, propagating in the laser field and re-colliding with the parent ion where the interference occurs. Slightly modifying (gating) the phase of the

19th International Conference on Ultrafast Phenomena, 2014

ABSTRACT We studied the two-color HHG emission from xenon in the giant resonance spectral region.... more ABSTRACT We studied the two-color HHG emission from xenon in the giant resonance spectral region. We found a substantial departure from the behavior expected for the single-active-electron picture which could be ascribed to electron correlation effects.

19th International Conference on Ultrafast Phenomena, 2014

ABSTRACT Extending the dimensionality of high harmonic generation (HHG) measurements has the pote... more ABSTRACT Extending the dimensionality of high harmonic generation (HHG) measurements has the potential to reconstruct structural features in molecules and resolve multielectron dynamics on attosecond time scales. We demonstrate that structural and dynamical effects in molecules can be unambiguously distinguished using multidimensional HHG techniques.

Strong field transient grating spectroscopy has shown to be a very versatile tool in time-resolve... more Strong field transient grating spectroscopy has shown to be a very versatile tool in time-resolved molecular spectroscopy. Here we use this technique to investigate the high-order harmonic generation from SF6 molecules vibrationally excited by impulsive stimulated Raman scattering. Transient grating spectroscopy enables us to reveal clear modulations of the harmonic emission. This heterodyne detection shows that the harmonic emission generated between 14 to 26 eV is mainly sensitive to two among the three active Raman modes in SF6, i.e. the strongest and fully symmetric υ1-A1g mode (774 cm −1 , 43 fs) and the slowest mode υ5-T2g (524 cm −1 , 63 fs). A time-frequency analysis of the harmonic emission reveals additional dynamics: the strength and central frequency of the υ1 mode oscillate with a frequency of 52 cm −1 (640 fs). This could be a signature of the vibration of dimers in the generating medium. Harmonic 11 shows a remarkable behavior, oscillating in opposite phase, both on the fast (774 cm −1 ) and slow (52 cm −1 ) timescales, which indicates a strong modulation of the recombination matrix element as a function of the nuclear geometry. These results demonstrate that the high sensitivity of high-order harmonic generation to molecular vibrations, associated to the high sensitivity of transient grating spectroscopy, make their combination a unique tool to probe vibrational dynamics.

Optics express, Jan 20, 2014

Phase measurement is a long-standing challenge in a wide range of applications, from X-ray imagin... more Phase measurement is a long-standing challenge in a wide range of applications, from X-ray imaging to astrophysics and spectroscopy. While in some scenarios the phase is resolved by an interferometric measurement, in others it is reconstructed via numerical optimization, based on some a-priori knowledge about the signal. The latter commonly use iterative algorithms, and thus have to deal with their convergence, stagnation, and robustness to noise. Here we combine these two approaches and present a new scheme, termed double blind Fourier holography, providing an efficient solution to the phase problem in two dimensions, by solving a system of linear equations. We present and experimentally demonstrate our approach for the case of lens-less imaging.

Uvx 2008: 9e Colloque Sur Les Sources Coherentes Et Incoherentes Uv, Vuv Et X; Applications Et Developpements Recents, 2008

ABSTRACT The high order harmonic generation process from molecules can be used to probe the struc... more ABSTRACT The high order harmonic generation process from molecules can be used to probe the structure of the emitting medium with high spatial resolution [1,2]. The measurements of molecular dynamics with such a probe is thus very appealing. Contrast is an important issue in pump probe spectroscopy: in general the probe only excites part of the molecules, so that the detected signal can be dominated by contributions from non-excited molecules. In this article we review two techniques that can be used to enhance the contrast of pump probe measurements: transient grating, spectroscopy and polarization-resolved spectroscopy. We use these techniques to detect rotational wavepackets and demonstrate a dramatic improvement in the contrast of the measured signal.

International Conference on Ultrafast Phenomena, 2010

ABSTRACT

Physical Review Letters, 2013

In strong-field light-matter interactions, the strong laser field dominates the dynamics. However... more In strong-field light-matter interactions, the strong laser field dominates the dynamics. However, recent experiments indicate that the Coulomb force can play an important role as well. In this Letter, we have studied the photoelectron momentum distributions produced from noble gases in elliptically polarized, 800 nm laser light. By performing a complete mapping of the three-dimensional electron momentum, we find that Coulomb focusing significantly narrows the lateral momentum spread. We find a surprisingly sensitive dependence of Coulomb focusing on the initial transverse momentum distribution, i.e., the momentum at the moment of birth of the photoelectron. We also observe a strong signature of the low-energy structure in the above threshold ionization spectrum.

Physical Review A, 2004

In spectroscopy, the fingerprint of a substance is usually comprised of a sequence of spectral li... more In spectroscopy, the fingerprint of a substance is usually comprised of a sequence of spectral lines with characteristic frequencies and strengths. Identification of substances often involves postprocessing, where the measured spectrum is compared with tabulated fingerprint spectra. Here we suggest a scheme for nonlinear spectroscopy, where, through coherent control of the nonlinear process, the information from the entire spectrum can

Nature Physics, 2006

Generating attosecond pulses has required a radically different approach from previous ultrafast ... more Generating attosecond pulses has required a radically different approach from previous ultrafast optical methods.

IEEE Journal of Quantum Electronics, 2001

Abstract—Under certain conditions, a high-finesse resonance phenomenon can occur in a grating wav... more Abstract—Under certain conditions, a high-finesse resonance phenomenon can occur in a grating waveguide structure (GWS). By varying these conditions, a shift in the resonance wavelength can be achieved. Specifically, utilizing the high finesse property of the GWS, small ...