2D-smoothing of laser beam fluctuations in optical compressor

We propose a modification of the four diffraction gratings Treacy compressor (TC)—a double-smoothing grating compressor (DSGC)—which enables smoothing of spatial fluctuations of a laser beam in two directions. Smoothing along the groves is due to oblique incidence on the gratings or tilted grooves. Smoothing in the direction normal to the grooves is achieved due to the use of nonidentical pairs of gratings. It is shown that the far-field fluence and the focal beam intensity after the DSGC are like those after the TC. Smoothing is a consequence of spatial harmonics lagging behind or overtaking the main pulse in proportion to the transverse wave vector. Analytical expressions are obtained for the spectrum of fluence fluctuations and fluence rms at the DSGC output. The efficiency of suppressing small-scale self-focusing in transmissive optical elements after the DSGC, for example, in the case of post-pulse compression is assessed.