Generation of the second and third harmonics of the radiation of a subpicosecond neodymium laser with a 1012 contrast on a metal target

A neodymium laser with a master Raman oscillator, generating pulses of 0.8 ps duration and of 10¹² contrast, was used to study harmonic generation by the interaction of radiation of 10¹⁵ – 10¹⁶ W cm^–2 intensity with a metal target. When the laser pulse had the p polarisation (the angle of incidence of the radiation on the target was 45°C), the second and third harmonics were generated by anharmonic motion of electrons on the plane plasma — vacuum interface. The energy efficiencies of conversion to the second and third harmonics depended weakly on the laser radiation intensity I (they were proportional to I^0.2) and amounted to ~1.5 × 10^–5 and ~0.8 × 10^–5, respectively. When the pulse had the s polarisation, the generation efficiency fell by a factor of 10 for the second harmonicand by a factor more than 10³ for the third harmonic.