Comparison of high-order harmonic generation from various cluster- and ion-containing laser plasmas

We apply the technique of high-order harmonic generation from laser-produced plasma to investigate the harmonics generated from a medium that contains an abundance of micron-and sub-micron-sized structures. We compare harmonic efficiencies from the plasma plumes containing silver nanoparticles (110 nm spherical), colloidal silver (blocks of 100 - 1000 nm), aluminium particles (2 - 14 mu m) and copper oxide nanorods (50 nm thick, few mu m long). We compare these results with those obtained using solid bulk targets. We show that plasma media that are abundant with small-sized structures have higher harmonic generation efficiencies. Results also reveal that the harmonic cutoff is not affected significantly by using the nanostructured targets. The maximum conversion efficiency we observe is 4 x 10(-5) using silver nanoparticles.