Semi Automatic Cup Mask Forming Machine Ningbo Dokee Mask Machine Co., Ltd. , https://www.autrendsmac.com
Advances in research on the physical mechanism of stimulated Raman scattering by Shanghai Optomechanics
[ Instrument R&D of Instrumentation Network ] Recently, the Joint Laboratory of High Power Laser Physics of Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences has made new progress in the research of stimulated Raman scattering (SRS) physical mechanism, and discovered a new The non-intrinsic mode of stimulated Raman scattering provides new insights for the research in basic fields such as nonlinear physics, nonlinear optics and inertial confinement fusion. Related research results were published in "High Power Laser Science and Engineering" (High Power Laser Sci. Eng.).
It is generally believed that SRS occurs below a critical density (nc) of 0.25 and can only be excited by intrinsic mode. The eigenmode is an inherent mode of electron plasma waves. It is independent of the external driving source, and its frequency is called the eigenfrequency. Generally, the nonlinear vibration is that the driving source matches the intrinsic mode in the object, and then is amplified by resonance. When the driving intensity is large, the so-called "quasi-mode" is excited, and the frequency of the "quasi-mode" is related to the intensity of the incident light. The study found that when the incident light intensity is greater than a certain threshold, a new SRS extrinsic mode will be excited. The strong laser can excite the non-intrinsic electrostatic mode in the region above 0.25nc. The frequency of this mode is fixed at half the frequency of the incident light, which has nothing to do with the intrinsic frequency of the plasma and the driving source. At the same time, the group velocity of the generated electrostatic waves and scattered light is 0, so electromagnetic solitons and electrostatic solitons can be formed in the plasma. This process will consume the energy of the pump laser in inertial confinement fusion, and at the same time produce a large number of super hot electrons.
The research team introduced this new SRS mechanism from two aspects, theoretical analysis and numerical simulation, which are in good agreement. The simulation results are shown in the figure. When the incident light intensity exceeds the excitation threshold, an extrinsic SRS excitation will be found. The proposal of this mechanism will promote the study of nonlinear physics and provide a reference for the understanding and suppression of the laser plasma parametric process in the study of inertial confinement fusion.
The research work was supported by the Shanghai Sailing Project and the Strategic Pilot Technology Special Project (Category A) of the Chinese Academy of Sciences.