Experimental investigation on cross-beam energy transfer between P-polarized lasers at 45-deg incidence

In this paper, we report the first experimental results on cross-beam energy transfer (CBET) at the Shengguang-II laser facility, in which two p-polarized laser beams irradiated planar targets at 45-deg incidence orthogonally. Frequency shifts of 0 and 0.06% were added between the two beams to investigate the relation of CBET to the degree of frequency shift. Enhancement of scattering was observed in the two-beam configuration with respect to the sum of the two single-beam configurations, indicating CBET was developed by the interaction of the two beams in the cases both with and without the frequency shift. When time delays were added between the seed and the pump pulses, scatter from the seed was enhanced, which further confirmed the existence of CBET in the experiments. The amplifications of the seed light by CBET with and without the frequency shift were sequentially similar to 3.3 and similar to 2.0 when the two beams were synchronized, and the energy loss due to CBET within the full aperture of the final optics of the pump to the total laser energy was similar to 4% with the frequency shift. Calculations suggest that a more than 0.2% frequency shift may be needed to mitigate CBET under experimental laser-plasma conditions.