Abstract

During the interaction of an intense, sharply rising femtosecond laser pulse with the surface of a solid target a thin layer of plasma is formed in which the density falls from approximately solid density to vacuum in a very short distance. It has been recognized more than a decade ago that the dynamics of electrons driven across such a sharp plasma-vacuum boundary is highly nonlinear, giving rise to the generation of optical harmonics of high order¹-². With the extremely high laser intensity available today the laser-induced excursion of the electrons may reach a considerable fraction of the wavelength, and significant contributions to the electronic anharmonicity from relativistic effects come into play. The relativistic interaction regime offers higher efficiency and an extension of harmonic generation to much shorter wavelengths. Thus the generation of harmonics using a solid target is a promising tool for the generation of coherent beams of ultrashort soft x-ray pulses.

© 1996 Optical Society of America