Second harmonic generation of focused beams on the LFEX laser facility.

There is a strong demand for efficient second harmonic generation (SHG) in ultra-intense short-pulse lasers. This paper demonstrates the generation of an unconverted fundamental (1ω)+second harmonics (2ω) mixed laser on the LFEX laser system. The experimental setup utilizes 0.5 mm-thick LBO crystal plates in a focusing beams implemented after an off-axis parabola, the design reduces the size and cost of the SHG system. The LFEX laser beams with four-beams combined energy of 222 J and a pulse duration of 1.5 ps, is successfully converted to 102 J of 2ω light and 100 J of unconverted 1ω light, 20 J is lost through surface reflections, and they are mixed at the focal point. Verification of successful SHG is confirmed through X-ray pinhole imaging and electron spectrometry. This novel technique is not limited to LFEX lasers and holds applicability for various ultra-intense lasers. Consequently, this accomplishment significantly contributes to expanding the capability for high-energy density laser-plasma experiments.