Vacuum ultraviolet and terahertz pulse generation in bulk media and guided geometries based on plasma generating femtosecond light pulses
Final Report Abstract
During the project, new methods of THz and UV (VUV) in noble gases were studied. In particular, THz generation in high intensity femtosecond pump pulses in different geometries such as plasma spot, hollow gas-filled waveguide as well as filament were investigated. It was shown that in all these cases, at the pump energy level where THz generation is effective, the main role is played by plasma-induced nonlinearities, and the Kerr nonlinearity plays only a minor role. The important details and the structure of the THz spectrum formed during the light-induced ionization was discovered. Namely, it was shown that the THz spectrum ca be represented as a sum from the individual attosecond-time long ionization events arising near the maxima of the pump electric field. This framework allowed to clarify the details of dependence of THz spectrum on pump pulse parameters such as frequency, number of colors and pulse durations, and opened wide avenue to control the THz spectrum, shape and energy. In particular, the pump regimes with more than two pump frequencies were studied. It was shown that they may provide stronger conversion efficiency as well as much broader spectrum, giving rise to a supercontinuum spanning extremely large spectral interval from THz to near infrared. The important influence of the effects of pump propagation in the process of THz generation was discovered, leading to the spectral broadening in all the geometries studied in the project. Generation of short UV and VUV pulses based on phasematching originating from periodic variation of the gas pressure was studied. It was shown that the quasi-phase-matching in such system is, indeed, achievable giving rise to possibility to produce high energy sub-20-fs UV and VUV pulses.
Publications
- „Ultrafast Spatiotemporal Dynamics of Terahertz Generation by Ionizing Two-Color Femtosecond Pulses in Gases“, Physical Review Letters, vol. 105, p. 053903 (2010)
I. Babushkin, W. Kühn, C. Köhler, S. Skupin, L. Berge, K. Reimann, M. Woerner, J. Herrmann, and T. Elsaesser
- „Directionality of terahertz emission from photoinduced gas plasmas“, Optics Letters, vol. 36, p. 3166 (2011)
C. Köhler, E. Cabrera-Granado, I. Babushkin, L. Bergé, J. Herrmann, and S. Skupin
- „Tailoring terahertz radiation by controlling tunnel photoionization events in gases“, New Journal of Physics, vol. 13, p. 123029 (2011)
I. Babushkin, S. Skupin, A. Husakou, C. Kohler, E. Cabrera-Granado , L. Berge and J. Herrmann
- „Quasi-phase-matching for third harmonic generation in noble gases employing ultrasound“, Optics Express, vol. 20, p. 22753 (2012)
U. K. Sapaev, I. Babushkin, and J. Herrmann
(See online at https://doi.org/10.1364/OE.20.022753) - „3D Numerical Simulations of THz Generation by Two-Color Laser Filaments“, Physical Review Letters, vol. 110, p. 073901 (2013)
L. Berge, S. Skupin, Ch. Köhler, I. Babushkin, and J. Herrmann
(See online at https://doi.org/10.1103/PhysRevLett.110.073901) - „The fundamental solution of the unidirectional pulse propagation equation“, Journal of Mathematical Physics, vol. 55, p. 032903 (2014)
I. Babushkin and L. Berge
(See online at https://doi.org/10.1063/1.4868698)
