Investigation of high harmonic generation from laser ablated plumes of silver

Silver (Ag) is one of the important targets in the studies of high harmonic generation (HHG) in the laser-induced plasma due to the relatively high conversion generation efficiencies and cut-off energy. In this work, we study the dependence of HHG in plasma plumes of Ag as a function of various laser parameters, including intensity of ablation pulse, intensity and ellipticity of driving pulse, and the delay between the two pulses. We identify the type of ion that dominates the measured HHG spectra by comparing the experimental data with strong-field approximation simulations and classical calculations for Ag atoms, Ag+, and Ag2+ ions. We also perform a comparative HHG study between the plasmas of bulk Ag target and the plasmas of a nano-powders target. It is found that the harmonic yields in the latter case are higher over a wide range of the aforementioned laser parameters. The results also indicate that the number of nanoparticles in the plasma generated from a nano-powder sample is indeed significantly greater than that in the plasma from the bulk sample.

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