Wavelength Scaling of High Harmonic Generation Close to the Multiphoton Ionization Regime

Chien-Jen Lai, Giovanni Cirmi, Kyung-Han Hong, Jeffrey Moses, Shu-Wei Huang, Eduardo Granados, Phillip Keathley, Siddharth Bhardwaj, and Franz X. Kärtner
Phys. Rev. Lett. 111, 073901 – Published 12 August 2013

Abstract

We study the wavelength scaling of high harmonic generation efficiency with visible driver wavelengths in the transition between the tunneling and the multiphoton ionization regimes where the Keldysh parameter is around unity. Our experiment shows a less dramatic wavelength scaling of efficiency than the conventional case for near- and mid-IR driver wavelengths, and it is well explained by a generalized three-step model for increased Keldysh parameters that employs complex ionization times in addition to the nonadiabatic ionization. The complex ionization time is critical to avoid the divergence when replacing the quasistatic ionization model by the more general nonadiabatic ionization model. Together, the two modifications present a consistent description of the influence of the atomic potential on the rescattering process in the intermediate Keldysh regime.

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  • Received 21 February 2013

DOI:https://doi.org/10.1103/PhysRevLett.111.073901

© 2013 American Physical Society

Authors & Affiliations

Chien-Jen Lai1,*, Giovanni Cirmi1,2, Kyung-Han Hong1, Jeffrey Moses1, Shu-Wei Huang1, Eduardo Granados1, Phillip Keathley1, Siddharth Bhardwaj1, and Franz X. Kärtner1,2

  • 1Department of Electrical Engineering and Computer Science and Research Laboratory of Electronics, Massachusetts Institute of Technology (MIT), Cambridge, Massachusetts 02139, USA
  • 2Center for Free-Electron Laser Science, DESY, and Department of Physics, University of Hamburg, D-22607 Hamburg, Germany

  • *cjlai@mit.edu

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Vol. 111, Iss. 7 — 16 August 2013

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