APS : Long-range propagation of ultrafast ionizing laser pulses in a resonant nonlinear medium

Demeter, G.; Bachmann, A.-M.; Aladi, M.; Kedves, M.Á.; Fedosseev, V.; Gessner, S.; Braunmüller, F.; Muggli, P.; Moody, J.T.; Verra, L.; Panuganti, H.; Della Porta, G. Zevi; Lee, V.; Djotyan, G.P.; Ráczkevi, B.; Öz, E.; Hüther, M.; Batsch, F.; Guran, E.; Friebel, F.; Granados, E.; Martyanov, M.

doi:10.1103/PhysRevA.104.033506

Article
Report number	arXiv:2103.14530
Title	Long-range propagation of ultrafast ionizing laser pulses in a resonant nonlinear medium
Author(s)	Demeter, G. (Wigner RCP, Budapest) ; Moody, J.T. (Munich, Max Planck Inst.) ; Aladi, M. (Wigner RCP, Budapest) ; Bachmann, A.-M. (Munich, Max Planck Inst.) ; Batsch, F. (Munich, Max Planck Inst.) ; Braunmüller, F. (Munich, Max Planck Inst.) ; Djotyan, G.P. (Wigner RCP, Budapest) ; Fedosseev, V. (CERN) ; Friebel, F. (CERN) ; Gessner, S. ; Granados, E. (CERN) ; Guran, E. (Munich, Max Planck Inst.) ; Hüther, M. (Munich, Max Planck Inst.) ; Kedves, M.Á. (Wigner RCP, Budapest) ; Lee, V. (U. Colorado, Boulder) ; Martyanov, M. (CERN ; Munich, Max Planck Inst.) ; Muggli, P. (Munich, Max Planck Inst.) ; Öz, E. (Munich, Max Planck Inst.) ; Panuganti, H. (CERN) ; Ráczkevi, B. (Wigner RCP, Budapest) ; Verra, L. (CERN ; Munich, Max Planck Inst. ; Munich, Tech. U.) ; Della Porta, G. Zevi (CERN)
Publication	2021-09-07
Imprint	2021-03-26
Number of pages	13
Note	12 pages, 10 Figures
In:	Phys. Rev. A 104 (2021) 033506
DOI	10.1103/PhysRevA.104.033506 (publication)
Subject category	physics.plasm-ph ; Other Fields of Physics ; physics.optics ; Other Fields of Physics
Accelerator/Facility, Experiment	CERN AWAKE
Abstract	We study the propagation of 0.05-1 TW power, ultrafast laser pulses in a 10 meter long rubidium vapor cell. The central wavelength of the laser is resonant with the $D_2$ line of rubidium and the peak intensity in the $10^{12}-10^{14} W/cm^2$ range, enough to create a plasma channel with single electron ionization. We observe the absorption of the laser pulse for low energy, a regime of transverse confinement of the laser beam by the strong resonant nonlinearity for higher energies and the transverse broadening of the output beam when the nonlinearity is saturated due to full medium ionization. We compare experimental observations of transmitted pulse energy and transverse fluence profile with the results of computer simulations modeling pulse propagation. We find a qualitative agreement between theory and experiment that corroborates the validity of our propagation model. While the quantitative differences are substantial, the results show that the model can be used to interpret the observed phenomena in terms of self-focusing and channeling of the laser pulses by the saturable nonlinearity and the transparency of the fully ionized medium along the propagation axis.
Copyright/License	preprint: (License: arXiv nonexclusive-distrib 1.0) publication: © 2021-2024 authors (License: CC BY 4.0)

$Sketch of the experimental setup. $E_{in}$ and $E_{out}$ are the input and output energy meters, respectively. Cameras in the virtual laser line correspond to the vapor chamber entrance (C1), center (C2) and exit (C3). Transmitted light distribution is detected by the pickoff camera after the imaging telescope (T). Images below the cameras are illustrative images from a single pulse measurement. Optical paths are not drawn to scale, the optical path from the final focusing telescope of the Ti:Sa laser to the vapor source entrance (and the C1 camera) is $\approx$40 m.$ $Width parameter $\sigma$ from Gaussian fit for transmitted laser pulses, $\mathcal{N}=6.6\cdot 10^{14}\mathrm{cm}^{-3}$. Mean values of binned data shown with asymmetric standard deviation indicated. Insets depict pickoff camera images for selected shots with: a) $E_{in}=15.6\mathrm{~mJ}$, b)-d) $E_{in}=26\mathrm{~mJ}$, e) $E_{in}=38\mathrm{~mJ}$ and f) $E_{in}=100\mathrm{~mJ}$, each also marked by the arrows. Aspect ratio of the insets corresponds to the detector physical aspect ratio, color coding of individual images are unique, scaled to individual image maxima. Inset g) depicts the virtual exit camera image (C3) for $E_{in}=38\mathrm{~mJ}$, drawn to the same spatial scale.$ $a) Width parameter $\sigma$ for transmitted pulse and virtual exit camera image as a function of input pulse energy for $\mathcal{N}=6.6\cdot 10^{14}\mathrm{cm}^{-3}$ vapor density shots. b) Transmitted laser pulse energy (left axis) and peak fluence (right axis). The points depict averages of binned data, error bars mark the error of the mean. Vertical dotted lines mark the approximate domain boundaries, which are labeled as: `ST' for sub-threshold domain, `B' for breakthrough domain, `CB' for confined beam domain and `AT' for asymptotic transparency domain.$ Show more plots

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Record created 2021-09-22, last modified 2023-11-24

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