Low-order harmonic generation in metal ablation plasmas in nanosecond and picosecond laser regimes

Low-order harmonics, third and fifth, of IR (1064 nm) laser emission have been produced in laser ablation plasmas of the metals manganese, copper and silver. The harmonics were generated in a process triggered by laser ablation followed by frequency up-conversion of a fundamental laser beam that propagates parallel to the target surface. These studies were carried out in two temporal regimes by creating the ablation plasma using either nanosecond or picosecond pulses and then probing the plasma plume with pulses of the same duration. The spatiotemporal behavior of the generated harmonics was characterized and reveals the distinct composition and dynamics of the plasma species that act as nonlinear media, allowing the comparison of different processes that control the generation efficiency. These results serve to guide the choice of laser ablation plasmas to be used for efficient high harmonic generation of laser radiation. © 2012 American Institute of Physics.Funding has been provided by Ministry of Science and Innovation of Spain (MICINN) under Project CTQ2010-15680. M. L.-A. thanks CSIC for a JAE-Pre contract. M.O. and M.S. acknowledge CONSOLIDER CSD2007-00058 and CAM (Geomateriales P2009/MAT 1629) respectively for contracts. R.A.G., G.S.B., N.K.S., R.I.T. and T.U. thank the Academy of Sciences for the Developing World (TWAS) for partial support of these studies (TWAS Research Grant 09-113 RG/PHYS/AS G). Useful discussions with Dr. R. de Nalda are gratefully acknowledged.Peer Reviewe

Low- and high-order nonlinear optical characterization of C

Third- and higher-order nonlinear optical processes in fullerenes were studies to define the influence of low-order nonlinearities on the high-order harmonic generation in these media. We measured the nonlinear absorption coefficients of the C60:toluene solution using the 532 and 1064 nm, 50 ps pulses. The high-order harmonic generation was studied during propagation of the 790 nm, 150 fs pulses through the plasmas produced on surfaces containing fullerene powder. These studies have shown that the low-order nonlinearities of fullerenes have no impact on the generation of harmonics in such mediums in the vacuum ultraviolet range at optimal intensity of laser radiation