Grating compressor optimization aiming at maximum focal intensity of femtosecond laser pulses

Abstract

It is shown that the optimal geometry of a Treacy compressor is the full-aperture compressor, in which the beam size at the first diffraction grating is equal to its length. Despite the energy losses and greater size of the focal spot, such a compressor provides considerably higher (by 1.5–2 times) focal intensity than an energy lossless compressor. Decreasing the density of grooves from 1200–1400/mm to about 1000/mm also increases the focal intensity by tens of percent. The constructed theory is generalized to the full-aperture two-grating compressor, which is the best design due to the angle of incidence on the first grating being smaller than the Littrow angle. Two gratings with a length of 138 cm allow obtaining an intensity of 4.09 × 1024W/cm2 and 5.01 × 1024W/cm2 in the focus of F/2 parabola for the projects XCELS and SEL-100PW, reaching the 139 PW and 174 PW power.