Peculiarities of Harmonics Generated from Interaction of 27 ps Laser Radiation with Solid Aluminium Targets
Аннотация
Investigations on harmonic generation in laser-matter interaction of Nd:glass laser radiation (I ≤ 1.5 × 1015 W cm-2, τ = 27 ps) with solid aluminium surfaces have been performed. We present here some peculiarities of spectral, temporal and spatial characteristics of harmonic radiation (up to fourth harmonic), and compare these results with those reported for the shorter pulse duration regime. A power law scaling of 1.5, 1.8 and 3.8 and conversion efficiencies in the range of 10-8 to 10-12 for second, third and fourth harmonics were observed. Second harmonic pulse duration (23 ps) was close to that of the fundamental radiation. This radiation observed in the specular direction was spectrally broadened and red-shifted for laser intensities exceeding 1015 W cm-2. A ring-like spatial structure spatial shape was also observed in the second harmonic at the maximum laser intensity.