Two-beam femtosecond high-field interactions with a solid target. Surface modification and second harmonic generation under the conditions of surface electromagnetic wave excitation

Very intense interfering beams generated a high-temperature near-surface femtosecond plasma with periodically modulated parameters. The dynamics of the efficiency of diffraction by such an induced ‘grating’ was studied. A background-free method for measuring the duration of high-intensity laser pulses on the basis of noncollinear second-harmonic generation was demonstrated. An increase in the second-harmonic signal was observed for the first time under the conditions of resonant excitation of a surface electromagnetic wave by high-intensity radiation of femtosecond duration.