Control of the properties and diagnostics of a dense femtosecond plasma formed from modified targets

It was found that modification of the physical properties of the surface layer of a target makes it possible to control, effectively and within a wide range, the characteristics of a femtosecond laser plasma (temperature, degree of ionisation, emissivity, and nonlinear-optical susceptibility) at moderate intensities of 10¹⁵ — 10¹⁶ W cm^–2, which are optimal for promising laser-plasma femtosecond technologies. The targets used in an experimental investigation were a periodic structure (gratings), ultrafine freely suspended films, and porous materials. Potential applications of such targets at intensities above 10¹⁷ W cm^–2 were considered.