Dependence of the stimulated Raman scattering threshold in droplets on the temporal stretching of a nanosecond laser pulse

2008 ◽  
Vol 39 (6) ◽  
pp. 700-706 ◽  
Author(s):  
A. Malarski ◽  
A. Leipertz
Keyword(s):  
Laser Pulse ◽  
Raman Scattering ◽  
Stimulated Raman Scattering ◽  
Nanosecond Laser Pulse ◽  
Nanosecond Laser ◽  
Stimulated Raman

scholarly journals Scattering of Ginzburg–Frank and Cherenkov Types Under Self-Focusing of Nanosecond Laser Pulses in Liquids

2018 ◽  
Vol 63 (4) ◽  
pp. 285
Author(s):  
A. I. Ivanisik
Keyword(s):  
Raman Scattering ◽  
Phase Velocity ◽  
Stimulated Raman Scattering ◽  
Laser Pulses ◽  
Pulse Excitation ◽  
Nanosecond Laser Pulse ◽  
Nanosecond Laser ◽  
Self Focusing ◽  
Anti Stokes ◽  
Stimulated Raman

We study the dynamics of nonlinear optical processes such as self-focusing, self-phase modulation, and stimulated Raman scattering in Kerr-liquids under the nanosecond laser pulse excitation. The results prove the existence of the transition Ginzburg–Frank-type effect, which promotes the appearance of new spectral components of the laser radiation at the medium boundary. The generation of extended anti-Stokes frequency-angular bands of stimulated Raman scattering is explained. When the velocity of a self-focusing focal spot matches the phase velocity of the non-linear polarization at the anti-Stokes Raman frequency and the phase velocity of the scattered axial radiation, the most intense frequency-angular bands appear. They are described by the equations typical of the Cherenkov radiation.

scholarly journals Time evolution of stimulated Raman scattering and two-plasmon decay at laser intensities relevant for shock ignition in a hot plasma

2019 ◽  
Vol 7 ◽  
Author(s):  
G. Cristoforetti ◽  
L. Antonelli ◽  
D. Mancelli ◽  
S. Atzeni ◽  
F. Baffigi ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Raman Scattering ◽  
Inertial Confinement Fusion ◽  
Stimulated Raman Scattering ◽  
Critical Density ◽  
Time History ◽  
High Energy ◽  
Experimental Results ◽  
Stimulated Raman ◽  
Shock Ignition

Laser–plasma interaction (LPI) at intensities $10^{15}{-}10^{16}~\text{W}\cdot \text{cm}^{-2}$ is dominated by parametric instabilities which can be responsible for a significant amount of non-collisional absorption and generate large fluxes of high-energy nonthermal electrons. Such a regime is of paramount importance for inertial confinement fusion (ICF) and in particular for the shock ignition scheme. In this paper we report on an experiment carried out at the Prague Asterix Laser System (PALS) facility to investigate the extent and time history of stimulated Raman scattering (SRS) and two-plasmon decay (TPD) instabilities, driven by the interaction of an infrared laser pulse at an intensity ${\sim}1.2\times 10^{16}~\text{W}\cdot \text{cm}^{-2}$ with a ${\sim}100~\unicode[STIX]{x03BC}\text{m}$ scalelength plasma produced from irradiation of a flat plastic target. The laser pulse duration (300 ps) and the high value of plasma temperature ( ${\sim}4~\text{keV}$ ) expected from hydrodynamic simulations make these results interesting for a deeper understanding of LPI in shock ignition conditions. Experimental results show that absolute TPD/SRS, driven at a quarter of the critical density, and convective SRS, driven at lower plasma densities, are well separated in time, with absolute instabilities driven at early times of interaction and convective backward SRS emerging at the laser peak and persisting all over the tail of the pulse. Side-scattering SRS, driven at low plasma densities, is also clearly observed. Experimental results are compared to fully kinetic large-scale, two-dimensional simulations. Particle-in-cell results, beyond reproducing the framework delineated by the experimental measurements, reveal the importance of filamentation instability in ruling the onset of SRS and stimulated Brillouin scattering instabilities and confirm the crucial role of collisionless absorption in the LPI energy balance.

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