Suppression of stimulated Raman scattering in plasma by an ultra-wideband stochastic phase low-coherence laser

Abstract

Suppression of the stimulated Raman scattering (SRS) by a stochastic phase low-coherence laser (SPLL) in homogeneous plasma is investigated by theoretical analysis and one-dimensional particle-in-cell (PIC) simulation. A simple model is established, in which the SPLL is modeled as a combination of a monochromatic laser and a broadband laser. When the phase randomness increases, the bandwidth of SPLL is broadened and the energy proportion of the monochromatic laser component is reduced. PIC simulation shows that SPLL can suppress SRS well and effectively control the number and energy of hot electrons. Various phenomena in the nonlinear process, such as the nonlinear frequency shift, the competition between forward-scattering and back-scattering modes, are explained in details.

Spectral characteristics of laser-plasma instabilities with a broadband laser

“…More detailed studies revealed the principles of LPI suppression by laser bandwidth, including detuning the interaction between waves (such as CBET), [11] incoherently driving many small instabilities to replace a single strong one (such as TPD), [15] and inducing time-incoherently interrupted excitation of plasma waves. In recent years, great progress has been made in broadband laser techniques, [17][18][19] and many broadband laser schemes have been proposed, [14,[20][21][22][23][24] but most of them are established on the basis of large bandwidth. Due to the technical and engineering limitations of existing laser fa-cilities, they can hardly meet the requirement on such a level of bandwidth, so the schemes mostly stay in the theoretical and simulation stages.…”