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Register a new userAnti-Stokes scattering and Stokes scattering of stimulated Brillouin scattering cascade in high-intensity laser-plasmas interaction
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The anti-Stokes scattering and Stokes scattering in stimulated Brillouin scattering (SBS) cascade have been researched by the Vlasov-Maxwell simulation. In the high-intensity laser-plasmas interaction, the stimulated anti-Stokes Brillouin scattering (SABS) will occur after the second stage SBS rescattering. The mechanism of SABS has been put forward to explain this phenomenon. And the SABS will compete with the SBS rescattering to determine the total SBS reflectivity. Thus, the SBS rescattering including the SABS is an important saturation mechanism of SBS, and should be taken into account in the high-intensity laser-plasmas interaction.
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The strong-coupling mode, called quasimode, will be excited by stimulated Brillouin scattering (SBS) in high-intensity laser-plasma interaction. And SBS of quasimode will compete with SBS of fast mode (or slow mode) in multi-ion species plasmas, thus leading to a low-frequency burst behavior of SBS reflectivity. The competition of quasimode and ion-acoustic wave (IAW) is an important saturation mechanism of SBS in high-intensity laser-plasma interaction. These results give a clear explanation to the low-frequency periodic burst behavior of SBS and should be considered as a saturation mechanism of SBS in high-intensity laser-plasma interaction.
The presence of multiple ion species can add additional branches to the IAW dispersion relation and change the Landau damping significantly. Different IAW modes excited by stimulated Brillouin scattering (SBS) and different SBS behaviors in several typical ignition hohlraum plasmas in the high-temperature and high-density region have been researched by Vlasov-Maxwell simulation. The slow mode in HeH or CH plasmas is the least damped mode and will be excited in SBS, while the fast mode in AuB plasmas is the least damped mode and will be excited in SBS. Due to strong Landau damping, the SBS in H or HeH plasmas is strong convective instability, while the SBS in AuB plasmas is absolute instability due to the weak Landau damping. However, although the SBS in CH plasmas is weak convective instability in the linear theory, the SBS will transform into absolute instability due to decreasing linear Landau damping by particles trapping. These results give a detail research of the IAW modes excitation and the properties of SBS in different species plasmas, thus providing the possibility of controlling SBS by increasing the linear Landau damping of the IAW by changing ion species.
Plasma-based parametric amplification using stimulated Brillouin scattering offers a route to coherent x-ray pulses orders-of-magnitude more intense than those of the brightest available sources. Brillouin amplification permits amplification of shorter wavelengths with lower pump intensities than Raman amplification, which Landau and collisional damping limit in the x-ray regime. Analytic predictions, numerical solutions of the three-wave coupling equations, and particle-in-cell simulations suggest that Brillouin amplification in solid-density plasmas will allow compression of current x-ray free electron laser pulses to sub-femtosecond durations and unprecedented intensities.
We compute the SBS gain for a metamaterial comprising a cubic lattice of dielectric spheres suspended in a background dielectric material. Theoretical methods are presented to calculate the optical, acoustic, and opto-acoustic parameters that describe the SBS properties of the material at long wavelengths. Using the electromagnetic and strain energy densities we accurately characterise the optical and acoustic properties of the metamaterial. From a combination of energy density methods and perturbation theory, we recover the appropriate terms of the photoelastic tensor for the metamaterial. We demonstrate that electrostriction is not necessarily the dominant mechanism in the enhancement and suppression of the SBS gain coefficient in a metamaterial, and that other parameters, such as the Brillouin linewidth, can dominate instead. Examples are presented that exhibit an order of magnitude enhancement in the SBS gain as well as perfect suppression.
We make systematic measurements of Raman anti-Stokes/Stokes (aS/S) ratios using two different laser excitations (514 and 633 nm) of rhodamine 6G (RH6G) on dried Ag colloids over a wide range of temperatures (100 to 350 K). We show that a temperature scan allows the separation of the contributions to the aS/S ratios from {it resonance effects} and {it heating/pumping}, thus decoupling the two main aspects of the problem. The temperature rise is found to be larger when employing the 633 nm laser. In addition, we find evidence for mode specific vibrational pumping at higher laser power densities. We analyze our results in the framework of ongoing discussion on laser heating/pumping under SERS conditions.
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