Analysis of spherical target illumination with partially coherent light through random phase plate

To improve the laser irradiation uniformity on a spherical target in inertial confinement fusion research, partially coherent light (PCL) with an angular spectral dispersion was introduced into a high power laser system. The calculation procedure is presented to estimate the irradiation nonuniformity which depends on the coherence of the beam pattern on the target plane. The theoretical analysis of smoothing effect of PCL using a random phase plate is compared with the experimental results. The reduction factor of irradiation nonuniformity is defined as the ratio of the Legendre-mode amplitude of the intensity distribution of PCL to that of the coherent laser. The mode structures predicted from reduction factors were consistent with the experimental results for different values of spatial and temporal coherence of PCL.