Analytic Description of the High-Energy Plateau in Harmonic Generation by Atoms: Can the Harmonic Power Increase with Increasing Laser Wavelengths?

Department of Physics, Voronezh State University, Voronezh 394006, Russia.
Physical Review Letters (Impact Factor: 7.51). 07/2009; 102(24):243901. DOI: 10.1103/PhysRevLett.102.243901
Source: PubMed


A closed-form analytic formula for high-order harmonic generation (HHG) rates for atoms (that generalizes an HHG formula for negative ions [M. V. Frolov, J. Phys. B 42, 035601 (2009)10.1088/0953-4075/42/3/035601]) is used to study laser wavelength scaling of the HHG yield for harmonic energies in the cutoff region of the HHG plateau. We predict increases of the harmonic power for HHG by Ar, Kr, and Xe with increasing wavelength lambda over atom-specific intervals of lambda in the infrared region, lambda approximately (0.8-2.0) microm.

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    • "If the ponderomotive energy U p is kept fixed instead of the intensity, the HHG yield decreases exponentially with λ [19]. In contrast to these two cases, however, if harmonic energies are not fixed, the HHG yield for a fixed intensity may even increase with increasing wavelength λ due to atomic structure effects [20]. Systematic study of the wavelength dependence of the HHG yield began with investigations of the fine-scale oscillations in the λ dependence of integrated harmonic yields [15] [16] [17] [18]. "
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    • "Thus, the final step in HHG can be seen as the inverse process to photoionization. Therefore, the amplitude of the harmonics obtained in a single shot measurement can contain information about the inverse process; a bound electron absorbing a photon of energy e and going to the continuum [5] [1] [6]. This relationship can be exploited to retrieve, in a table top experiment, information about the photoionization cross section of molecules and atoms in the XUV regime. "
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