Observation of blueshift on harmonic generation from subpicosecond laser produced solid surface plasmas

Harmonic generation from solid surface plasmas is studied using a 475 fs Nd: Glass laser system. We observe that for a 45 degrees angle of incidence, the second harmonic is blue shifted by 1.6 nm, and the fifth harmonic is blue shifted by 5.1 nm for p-polarization at the intensity of 1 x 1017 Wcm-2. Furthermore, we find out that the blueshift distance is increased with orders of harmonic. The blueshift is interpreted as the collisionless absorption due to the anomalous skin effect. We also observe that the ratio between the harmonics intensities produced by p-polarized and s-polarized pump were 8 and 2 for the second and fifth harmonics. respectively at pump intensities 1 below 1017 W cm-2. The same ratio decreased to 0.8 and 0.5 for 1 > 2 x 1017 W cm-2