Mitigating parametric instabilities in plasmas by sunlight-like lasers

Sunlight-like lasers that have a continuous broad frequency spectrum, random phase spectrum, and random polarization are formulated theoretically. With a sunlight-like laser beam consisting of a sequence of temporal speckles, the resonant three-wave coupling that underlies parametric instabilities in laser-plasma interactions can be greatly degraded owing to the limited duration of each speckle and the frequency shift between two adjacent speckles. The wave coupling can be further weakened by the random polarization of such beams. Numerical simulations demonstrate that the intensity threshold of stimulated Raman scattering in homogeneous plasmas can be doubled by using a sunlight-like laser beam with a relative bandwidth of similar to 1% as compared with a monochromatic laser beam. Consequently, the hot-electron generation harmful to inertial confinement fusion can be effectively controlled by using sunlight-like laser drivers. Such drivers may be realized in the next generation of broadband lasers by combining two or more broadband beams with independent phase spectra or by applying polarization smoothing to a single broadband beam.

Automated summary

Theoretical formulation of sunlight-like lasers with continuous broad frequency spectrum, random phase spectrum, and random polarization has been proposed. Numerical simulations show that using sunlight-like laser beams with a relative bandwidth of around 1% can effectively control the intensity threshold of stimulated Raman scattering, reducing the generation of hot electrons harmful to inertial confinement fusion. This has significant implications for the future development of laser technology.