Second harmonic generation at large B-integral for ELI-class laser pulses

The created theory of second harmonic generation under strong influence of cubic polarization was experimentally verified. The 35% energy conversion efficiency of second harmonic generation in 0.6 mm KDP crystal at input average intensity 2 TW/cm2 was experimentally achieved. No optical breakdown was observed in 1mm KDP crystal at peak intensity 5 TW/cm2 (B-integral is 6) close to output intensity of multi-petawatt lasers including Extreme Light Infrastructure (ELI) project The comparable analyze of second harmonic generation of radiations with fundamental wave lengths 910 nm and 800 nm evidently shows the major advantage of the first one. The double-pass scheme of second harmonic generation may be useful especially for 800 nm fundamental wave length.