Speaker
Abel Hailu Woldegeorgis
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P5.2029.pdf
MV/cm longitudinal terahertz fields from relativistic laser-overdense
plasma interactions
A. Woldegeorgis1, 2, T. Kurihara3, M. Almassarani1, 2, R. Große2, B. Beleites2, F. Ronneberger2,
G. G. Paulus1, 2, A. Gopal1, 2
1
Helmholtz-Institut Jena, Jena, Germany
2
Friedrich-Schiller-Universität Jena, IOQ, Jena, Germany
3
University of Konstanz, Konstanz, Germany
High-power broadband terahertz (THz) radiation can be generated when intense laser pulses
interact with matter. When the intensity of the laser pulse is higher than the ionization potential,
plasma is generated. The charged particle dynamics and the resultant quasi-static fields and
currents generated inside the plasma can give rise to broadband electromagnetic radiation
ranging from x-rays to THz radiation. In our work we focus on the generation of THz radiation
from such an interaction, in particular from the rear surface of a metal foil when its front surface
is shined with a TW laser pulse. Here radially polarized THz radiation is generated by the
transient dynamics of charged particles exiting the rear surface. Focusing a radially polarized
beam, compared to a beam with linear polarization, creates a strong and tightly focused
longitudinal field. It has been shown that longitudinal THz fields have a promising potential in
particle acceleration1. To date, few groups have reported on longitudinally polarized THz wave
generation with field strengths in the order of a few kV/cm 2. Here we report on the generation
and detection of longitudinally polarized THz pulses with field strength in excess of 1.5 MV/cm
from the rear surface of a thin foil irradiated by TW laser pulses. A transverse component with
field amplitude of 3 MV/cm was also measured. Noncollinear pump-probe electrooptic
technique was deployed to estimate the peak electric field strength, and study the temporal and
spectral properties. We employed two crystal geometries to detect the polarization of the
propagating THz pulses at the focus.
Fig 1. Temporal waveform of the transverse (Eρ)
and longitudinal (Ez) field components measured
using gallium phosphide (GaP) 110- and 100-cut
crystal respectively; inset shows the corresponding
normalized spectral amplitudes.
References
[1] E. Nanni et al., Nat. Commun. 6, 8486, 2015.
[2] Y. Minami et al., APL 102, 151106, 2013; M. J.
Cliffe et al., APL 105, 191112, 2014; M. J. Cliffe et
al., APL 108, 221102, 2016.
