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8THz-I-19
Theory of High Harmonics Generation in Extended Gas Media by Femtosecond Laser Field Having Different Wavelengths
S. Stremoukhov
Faculty of Physics, Lomonosov Moscow State University, Leninskie Gory, 1, build.2, 119991, Moscow, Russia National Research Centre "Kurchatov Institute", pl. Akademika Kurchatova, 1, Moscow, 123182 Russia
email: sustrem @gmail.com
Scaling wavelength of the laser driver radiation towards the mid-IR range is one of the most attractive methods of enlargement of the generated in gas harmonics spectra, while it width is ~ [1]. However, the efficiency of the generated harmonics scales as ^-55 [2]. Here, we discuss one of the possible ways to increase the harmonics photon flux using the effects of quasi-phase matching (QPM) for high harmonics generated in periodic media [3,4].
The problem has been investigated in the frame of the interference model of extended gas [5] and the non-perturbative theory of single atom response [6]. In numerical simulations, we suppose that the perforated gas media consists of a number of gas jets having spatial sizes d divided by free spaces forming the multi gas media. It interacts with a two-color (œ+2œ) laser field consisting of two linearly polarized components with zero degree angle between their polarization directions. Laser field wavelength scales from a near IR (800 nm) to a far IR (up to 15 mkm) spectral diapason.
The numerical calculations show that due to the QPM, the group of harmonics enhanced. The influence of the gas media parameters and the laser wavelength on the position of enhanced harmonics and its value is analyzed. The simple relations between the position of the enhanced QPM harmonics, laser wavelength and gas media parameters are introduced. Boundaries of the harmonics enhancement method are discussed.
The work was partially supported by the RFBR under Projects Nos. 18-02-40014 and 19-29-12030.
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