Experimental Evidence of Short Light Pulse Amplification Using Strong-Coupling Stimulated Brillouin Scattering in the Pump Depletion Regime

Abstract

The energy transfer from a long (3.5 ps) pump pulse to a short (400 fs) seed pulse due to stimulated Brillouin backscattering in the strong-coupling regime is investigated. The two pulses, both at the same wavelength of 1.057 microm are quasicounterpropagating in a preformed underdense plasma. Relative amplification factors for the seed pulse of up to 32 are obtained. The maximum obtained amplified energy is 60 mJ. Simulations are in agreement with the experimental results and suggest paths for further improvement of the amplification scheme.

Demonstration of laser pulse amplification by stimulated Brillouin scattering

“…These findings are corroborated by 1D numerical simulations using the particlein-cell code OSIRIS [5] , confirming that for sufficiently short pulses the necessary Brillouin downshifted frequency is presented in the laser bandwidth, therefore negating the requirement for a frequency downshift in the seed pulse to be performed before Brillouin scattering can be obtained. A pump-to-probe energy transfer of up to 2.5% has been obtained, which confirms earlier results by Lancia et al [6] , who obtained 2.25% in a similar experiment.…”

“…In addition to this, more energy can be transferred into the scattered wave via Brillouin scattering than via Raman scattering as less energy is coupled into the ionacoustic wave in Brillouin scattering than the Langmuir wave associated with Raman scattering. This makes the Brillouin mechanism particularly useful for applications such as laser amplification techniques [6,9] and induced energy transfer between adjacent laser beams at facilities such as the National Ignition Facility [10,11] .…”

Short-pulse amplification by strongly coupled stimulated Brillouin scattering

“…Other works have considered relativistic [44], thermal [58], and collisional [50] effects, as well as the role of instabilities like forward Raman scattering (FRS) [51] on the amplification process. SBS has been demonstrated experimentally [43,52,59], with recently published work suggesting amplification in the self-similar regime, where depletion of the pump beam is significant [59].…”

“…Currently, experimentally demonstrated performance of Raman amplifiers [30] exceeds that of Brillouin amplifiers [43,59] in energy transfer efficiency and peak amplified seed intensity, though higher total energy transfer between pump and seed has been achieved with SBS [59].…”

“…Initial study of amplification by SC-SBS considered plasma densities above one quarter of the critical density, where SRS is suppressed, but in an effort to avoid deleterious instabilities, particularly filamentation, study has expanded to include lower plasma densities, where SBS is in direct competition with SRS [43,45,46,51]. In this regime, the dominant amplification mechanism may not be obvious [62], and some care must be taken to determine the underlying process.…”