We conduct a comparative numerical study of the formation of closely located light spots in the focal plane of diffraction gratings and binary optical elements matched with Hermite-Gaussian modes and specular Airy beams. It is shown that while gratings allow a set of uniform focal spots to be generated with high accuracy, the resulting pattern quickly deteriorates when displaced from the focal plane. Due to their modal properties, Hermite-Gaussian beams are low-sensitive to defocusing, but produce focal spots different in size and intensity. Specular Airy beams offer a tradeoff solution-they produce a more uniform intensity pattern of light spots than the HermiteGaussian modes, at the same time showing a lower sensitivity to defocusing. Experiments with a tunable laser have confirmed the above-mentioned advantages of the specular Airy beams in comparison with the Hermite-Gaussian modes, also showing good spectral stability of the manufactured diffraction optics.

We present the results of experiments on generation of Hermite – Gaussian modes up to the third order inclusive using binary-phase diffractive optical elements (DOEs) illuminated by subterawatt femtosecond laser pulses. We perform a compariosn of the mode formation using DOEs designed by the kinoform method and the fractional coding technique, when the DOEs are illuminated by both femtosecond radiation and cw laser radiation at close wavelengths.

We perform a comparative numerical study of the formation of closely spaced focal spots in the focal plane with diffraction gratings and binary optical elements matched with the Hermite-Gaussian modes. It is shown that low-index modes provide the generation of good-quality focal spots and relative tolerance to chromatic dispersion. Experiments with pulsed and tunable lasers have shown that phase optical elements matched with TEM(1,0) and TEM(1,1) modes show promise for creation of arrays of closely spaced focal spots.

The possibility of surface microstructuring of melted and solid target by a weak femtosecond laser pulse is demonstrated. An appreciable increase of hot electron energy is observed in 3D PIC simulations of interaction of ultrashort laser pulse with modified surface of the target in a wide range on laser intensities. First experimental results on x-ray diagnostics of plasma, created onto the surface of microstructured solid and melted target are presented.