Intensity dependence of classical and collective absorption processes in laser produced plasmas at 1.053 μm and 0.527 μm

Intensity dependence of absorption efficiency in laser produced plasmas, at a pulse width of 100 ps, has been measured using an integrating spherical photometer at the laser irradiance of ≅-10¹⁴ ˜ 10¹⁶ W/cm² for the laser wavelengths of 1.053 μm and 0.527 μm, respectively. For these experimental conditions, the observed experimental results are well explained in terms of classical and collective absorption processes. Specifically, we propose the formation of periodic density profile modification in the underdense region which results in enhanced resonance absorption efficiency at high laser irradiance.