Application of 150 kHz Laser for High-Order Harmonic Generation in Different Plasmas

Application of high pulse repetition rate lasers opens the way for increasing the average flux of the high-order harmonics generating in the ions-and nanoparticles-containing plasmas ablated on the surfaces of various metal targets. We demonstrate the harmonic generation of 37 fs, 150 kHz, 1030 nm, 0.5 mJ pulses in different plasmas. The formation of plasma plumes on the surfaces of carbon, titanium, boron, zinc, and manganese targets was performed during laser ablation, using 250 fs pulses from the same laser. The ablation of the mixed powder of boron nanoparticles and silver microparticles was used for generation of harmonics with high yield. Harmonics up to the fortieth orders from the carbon plasma were obtained. The estimated conversion efficiencies in laser-produced plasmas were ≤10⁻⁵. The photon flux for a single harmonic generating in carbon plasma was estimated to be 8 × 10¹³ photons/s.