DFG-RSF:Controlled femtosecond super-filaments
Final Report Abstract
The recently discovered superfilaments exhibit unexpected high intensities and densities of free electrons, quite different to common filaments. They appear in merging processes of two or more filaments in complex multi-filament scenarios. These objects are of fundamental interest as their dynamics, properties, and deterministic generation mechanisms are barely known. They are also especially promising for applications as unprecedented high plasma densities came in reach. In this joint German-Russian project we investigated, both experimentally and theoretically, the generation of these superfilaments under controlled initial pulse and beam parameters, with focus on the efficient generation of THz radiation. The main experiments have been performed with a Ti:sapphire femtosecond terawatt laser system and have been compared to numerical simulations based on a 3D+1 code solving the forward Maxwell equation. We successfully demonstrated 3D spatial and energy dynamics of merging filaments exhibiting the characteristics of superfilaments and investigated the transition from a single air filament to the superfilament. We could determine the optimal focal length leading to maximal intensity of radiation inside a filament with regular structure. The dependencies of peak intensity and plasma density on propagation distance, transverse distributions of energy density and spatial spectra of radiation were investigated. We got deeper insight into the complex process of filament merging, which helped to exploit this process for generation of THz radiation. By loosely focusing a two-color beam in the air, we demonstrated efficient THz pulse generation with significant energy increase by increase of the focal length. In addition, we could demonstrate that a 2D array of multiple plasma filaments in atmospheric density gases is suitable for highly efficient generation of terahertz radiation. We revealed the dependence of THz radiation on the pump wavelength as well as on the degree of the gas pre-ionization. We showed that the sub-cycle attosecond dynamics of the ionization process plays a critical role in generation of the THz and higher-order harmonics. Our insight into superfilamentation pave directly the way for further modern applications such as remote sensing, laser-induced breakdown spectroscopy, discharge guiding, or attosecond imaging. We further believe that our findings build a solid base for a deeper investigation of complex high-intense ultrafast light-matter interactions. Besides aspects of superfilamentation, our investigations revealed several other important results concerning filamentation in general. We demonstrated a regularizing mechanism based on resonant radiation generation, which counteracts the collapse leading to unexpected long filament propagation. We defined and demonstrated a suitable value, referred to as ‘intra-pulse coherence’ giving insight into the relationship between different spectral components in highly complex spectral broadening scenarios. A further important result is a new concept enabling a binding mechanism between pulses at different center wavelengths, which is not induced by phase relations. This phenomenon is mainly unknown and opens up new perspectives for controlling and transferring light pulse energies.
Publications
- “Regularizing aperiodic cycles of resonant radiation in filament light bullets,“ Phys. Rev. Lett. 118, 163901 (2017)
C. Brée, I. Babushkin, U. Morgner, A. Demircan
(See online at https://doi.org/10.1103/physrevlett.118.163901) - “Symmetry breaking and strong persistent plasma currents via resonant destabilization of atoms,“ Phys. Rev. Lett. 119, 243202 (2017)
C. Brée, M. Hofmann, A. Demircan, U. Morgner, O. Kosareva, A. Savel’ev, A. Husakou, M. Ivanov, I. Babushkin
(See online at https://doi.org/10.1103/physrevlett.119.243202) - “Optimum chirp for efficient terahertz generation from twocolor femtosecond pulses in air” Appl. Phys. Lett. 113, 241103 (2018)
Zhen Zhang, N. Panov, V. Andreeva, Zhelin Zhang, A. Slepkov, D. Shipilo, M.D. Thomson, T.-J. Wang, I. Babushkin, A. Demircan, U. Morgner, Y. Chen, O. Kosareva, A. Savel'ev
(See online at https://doi.org/10.1063/1.5053893) - ”Polarization control of terahertz radiation from two-color femtosecond gas breakdown plasma” Opt. Lett. 43, 90 (2018)
O. Kosareva, M. Esaulkov, N. Panov, V. Andreeva, D. Shipilo, P. Solyankin, A. Demircan, I. Babushkin, V. Makarov, U. Morgner, A. Shkurinov, A. Savel’ev
(See online at https://doi.org/10.1364/ol.43.000090) - “ Soliton molecules with two frequencies,” Phys. Rev. Lett. 123, 243905 (2019)
O. Melchert, S. Willms, S. Bose, A. Yulin, B. Roth, F. Mitschke, U. Morgner, I. Babushkin, A. Demircan
(See online at https://doi.org/10.1103/physrevlett.123.243905) - ” Transverse structure and energy deposition by a subTW femtosecond laser in air: from single filament to superfilament,” New J. Phys. 21, 033027 (2019)
D. Pushkarev, E. Mitina, D. Shipilo, N. Panov, D. Uryupina, A. Ushakov, R. Volkov, A. Karabutov, I. Babushkin, A. Demircan, U. Morgner, O. Kosareva, A. Savel’ev
(See online at https://doi.org/10.1088/1367-2630/ab043f)
