Multi-µJ coherent extreme ultraviolet source generated from carbon using the plasma harmonic method.
We demonstrate intense high-order harmonic generation from plasma that is created from different carbon targets. We obtain high-order harmonic energy in the multi-microjoule range for each harmonic order from the 11th to the 17th harmonic. By analyzing the target morphology and the plasma composition, we conclude that the intense harmonics from the bulk carbon targets originate from nanoparticles target.
Multiple quasi-phase-matching for enhanced generation of selected high harmonics in aperiodic modulated fibers.
A technique for enhanced generation of selected high harmonics in a gas medium, in a high ionization limit, is proposed in this paper. An aperiodically corrugated hollow-core fiber is employed to modulate the intensity of the fundamental laser pulse along the direction of propagation, resulting in multiple quasi-phase-matched high harmonic emissions at the cutoff region. Simulated annealing (SA) algorithm is applied for optimizing the aperiodic hollow-core fiber. Our simulation shows that the yield of selected harmonics is increased equally by up to 2 orders of magnitude compared with no modulation and this permits flexible control of the quasi-phase-matched emission of selected harmonics by appropriate corrugation.
Many-electron effects in BaC60: Collective response and molecular effects in optical conductivity and photoionization.
The optical conductivity of BaC 60 is calculated using a model of an atom embedded inside a finite shell of jellium. The investigations are carried out within the framework of time-dependent local-density theory. The optical conductivity of C 60 shows a strong collective resonance (plasmon) at 17.6 eV, which is nearly degenerate with the Ba Sp-d giant dipole resonance, leading to strong interference effects in BaC 60 . Molecular multiple-scattering effects appear as prominent oscillations in the Ba 4d photoionization spectrum of BaC 60 , without any reduction of the overall intensity of the collective 4d-f giant dipole resonance