Research on beam smoothing characteristics using linearly modulated light

Precise physical experiments place strict requirements on target illumination uniformity. A new smoothing technology aimed at indirect-drive laser fusion is studied, which uses linearly modulated light and angular spectral dispersion (ASD). Simulation indicates that the best smoothing effect could be obtained when number of color cycles (N_c) is chosen to be 0.5 at 1.2 nm bandwidth. A table-top setup aimed at the experimental study of the beam smoothing method has been established. When the linearly modulated light generated by pulse stacking is dispersed by a grating with N_c=2.6, periodical undulations are found on the far-field focal spot, which agrees with the simulation results. To improve illumination uniformity, the N_c adopted should be decreased to 0.5. Simulation also indicates that the combination of linearly modulated light, angular spectral dispersion and a continuous phase plate could considerably improve the irradiation nonuniformity.