Research On The Beam Smoothing Technology In The Beam Focusing Of High-power Laser Driving Device

In the research of laser indirect-driven inertial confinement fusion,laser-plasma interactions can produce many parameter instabilities which have serious negative influence on the transformation efficiency from laser to X-ray and uniform irradiation on the D-T fuel capsule.Laser-plasma interactions are closely linked to laser beam properties and propose demand to the profile and uniformity of far-field laser beam intensity distribution.High-power laser driver may adopt beam array focusing on target which means many laser beams focusing on one point.Beam array focusing provides a new dimension to the control of light field on target.At the same time,multi-beam interference in beam array focusing may affect the uniformity of the focal spot.How to improve smoothing performance and the research of smoothed laser beam characteristics are important to the research of laser-plasma interactions,the suppression of laser-plasma instabilities and the progress of inertial confinement fusion research.This paper makes a brief introduction to the researches of mainstream beam smoothing technologies nowadays.The physical connotation of smoothing by spectral dispersion realizing smoothing of light field on target is expounded.The smoothing characteristics and limitation of SSD are theoretically analyzed.According to the tendency of high-power solid-state laser facilities adopting beam array focusing and the requirement of solving multi-beam interference problem,spatial smoothing and temporal smoothing methods in beam array focusing are discussed.The main innovative points are summarized as follows:1.Through the analysis of SSD beam's physical image,the physical connotation of SSD beam realizing smoothing of focal spot,which means the smoothing effect comes from the evolution of far-field primitive electric field phase with time,is expounded.The theoretical model of SSD smoothing performance is improved which means the smoothing performance of SSD is limited by both modulation depth and dispersion range.2.Based on the research of SSD beam,smoothing performance of multi-FM SSD insingle beam is analyzed,which proved that multi-FM SSD cannot achieve better smoothing performance than single-FM SSD with its best smoothing result.3.Bundle multiple-frequency-modulation smoothing by spectral dispersion technology is proposed.The feasibility of this method is proved by numerical simulation.The effect of two dimensional smoothing by spectral dispersion in beam array focusing to the uniformity of far-field distribution is studied.The researches in this paper provide new methods to the control of light field on target in high-power solid-state laser driver.