Suppression of stimulated Raman scattering by angularly incoherent light, towards a laser system of incoherence in all dimensions of time, space, and angle

Abstract

Laser–plasma instability (LPI) is one of the main obstacles to achieving predictable and reproducible fusion at high gain through laser-driven inertial confinement fusion (ICF). In this paper, for the first time, we show analytically and confirm with three-dimensional particle-in-cell simulations that angular incoherence provides suppression of the instability growth rate that is additional to and much stronger than that provided by the well-known temporal and spatial incoherence usually used in ICF studies. For the model used in our calculations, the maximum field ratio between the stimulated Raman scattering and the driving pulses drops from 0.2 for a Laguerre–Gaussian pulse with a single nonzero topological charge to 0.05 for a super light spring with an angular momentum spread and random relative phases. In particular, angular incoherence does not introduce extra undesirable hot electrons. This provides a novel method for suppressing LPI by using light with an angular momentum spread and paves the way towards a low-LPI laser system for inertial fusion energy with a super light spring of incoherence in all dimensions of time, space, and angle, and may open the door to the use of longer-wavelength lasers for inertial fusion energy.

Suppression of stimulated Raman scattering kinetic bursts by intensity-modulated broadband laser

“…2.1 宽带激光的统计特性 目前常见的宽带激光建模有调频宽带激光 [7,17] 、 叠加宽带激光 [8,11,15] 、随机相位宽带激光、近太阳 光 [18] 和角动量非相干光 [19] 等. 其中, 叠加宽带激 光(multi-beamlet laser, MBL)能够描述实验上宽 带激光频率、相位随机的特性, 被广泛用于LPI的 增长过程、不稳定性阈值等研究.…”

“…具体建模方法为在宽带激光电场 前 加入一个强度调制函数 , 该函数具有如下 形式: 会引发某些低频不稳定性过程, 如SBS和CBET 等 . 在 先 前 的 工 作 中 , Albright等 [4] , Afeyan 和 Hüller [25,26] 宽带激光设计相结合, 如解耦光 [8] 、近太阳光 [18] 、 弹簧光 [19] 等, 有望在更长时间、更大空间尺度上抑…”

Beijing Union Medical College Hospital and China’s Modern Medical Development

“…The SOV pulse [1] carrying longitudinal OAM parallel to the propagation direction has spiral wavefront phase of the form exp(iℓϕ), where ℓ represents the topological charge and ϕ is the azimuthal angle in the transverse plane. In past decades, researchers have extensively studied the generation of SOV pulse [2][3][4][5] and corresponding laser-matter interactions [6][7][8][9][10][11][12][13][14][15][16], especially the generation of γ-photons and pairs with longitudinal OAM [17][18][19][20][21][22][23][24][25][26][27][28][29]. Photons with OAM possesses an additional degree of freedom, which can expand the information capacity for optical communication [30], detect the inhomogeneities of small-scale interstellar medium, investigate OAM transfer in Kerr black holes [31,32] and so on.…”