High-order harmonic generation in plasmas from nanoparticle and mixed metal targets at 1-kHz repetition rate

High-order harmonic generation in laser-produced plasmas from nanoparticle and mixed metal targets is studied using a femtosecond Ti:sapphire laser operating at 1-kHz repetition rate. Mixed plasmas from brass and plasmas from nanoparticles (Al, carbon) are investigated and compared to their monatomic counterparts of Zn, Cu, and Al. The dependence on the delay between the heating ablation pulse and the driving converting pulse is studied for a light (carbon) and a heavy atom (silver) target. Further, we report on a comparative measurement of the efficiencies and the photon flux from argon gas harmonics and carbon plasma harmonics. For our conditions, the 13th harmonic is generated in a carbon plasma with an efficiency of η = 5.3 × 10−7 and yields a flux of about 9.8 × 1010 photons s−1, about 40 % higher than the corresponding harmonic flux in Ar gas under otherwise identical conditions.