Forward 2nd harmonic emission from laser plasma filaments
Authors: Deha I., Biancalana V., Bianconi F., Borghesi M., Chessa P., Giulietti A., Giulietti D., Gizzi LA., Nocera L., Schifano E.
Autors Affiliation: CNR, Ist Fis Atom & Molec, via Giardino 7, I-56127 Pisa, Italy;
Univ Sci & Technol Houari Boumedienne, Algiers, Algeria;
Univ Pisa, Dipartimento Fis, I-56100 Pisa, Italy;
Ecole Polytech, Utilizat Lasers Intenses Lab, F-75230 Paris 05, France
Abstract: Experimental observations are reported on the interaction of 1-mum laser light with underdense plasmas (n less-than-or-equal-to 0.25 n(c)) from thin foil plastic targets. Nominal laser intensity on target was up to 3 x 10(13) W/cm2 in a 3-ns pulse, but much higher intensity was reached due to spiky laser pulses. We studied forward-emitted second harmonic light as a diagnostic of the interaction and in particular of the occurrence of filamentation. Measurements included: energy monitoring of 2omega forward emission vs. target position and laser energy; time resolved (120-ps gate) imaging of the interaction region cross section. The second harmonic energy level was found to be sensitive to target position. In addition, the images obtained with the target in position of maximum second harmonic generation showed unstable structures whose scale length is comparable with the expected one for maximum filamentation growth. These results are shortly discussed in the framework of stationary filamentation theory and second harmonic generation in inhomogeneous media.
Journal/Review: LASER AND PARTICLE BEAMS
Volume: 10 (4) Pages from: 617 to: 627