Research of beam smoothing technology in high power laser driver (Invited)

In the process of laser driven inertial confinement fusion, the inhomogeneity of light field with different spatial frequencies will cause the hydrodynamic instability, imprinting and laser plasma instability in implosion. These instabilities will eventually affect the compression ratio of implosion, thus affecting the ignition. In order to control the focal spot nonuniformity and suppress instabilities, beam smoothing technology was proposed to control the beam target coupling process through light field control. Beam smoothing can be divided into spatial smoothing and temporal smoothing. Spatial smoothing can reduce the low-frequency inhomogeneity by controlling the wavefront shape. Temporal smoothing reduces the speckle in the focal spot by controlling the coherence of the laser beam, and then reduces the medium and high frequency inhomogeneity. With the increasing demand for laser-plasmas instability suppression at higher laser power density, some new beam smoothing methods have emerged. The application of beam smoothing technology in large laser facilities was introduced, and the currently proposed beam smoothing technologies were summarized and analyzed.