J. Phys. IV France 11 (2001) Pr2-369-Pr2-372
Enhancement of high-order harmonic generation efficiency by double pulse lasersA. Ishizawa, T. Kanai, T. Ozaki and H. Kuroda
Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
We have investigated the efficiency of the fifth order harmonics from solid surface plasma by varying the electron density gradient using two 2.2 ps, 1054 nm laser pulses. A prepulse irradiates the Al deposited target 0-20 ps prior to the arrival of the main Nd : Glass laser pulse in order to modify the electron density gradient. It is found that 5 ps time difference between the prepulse and main pulse results in an increase in the third harmonic signal by a factor of 2-3, which then decreases for time delays greater than 10 ps, and the fourth and fifth harmonic signal also increase. Experiments and calculations are presented that demonstrate a strong dependence of the conversion efficiency on the plasma scale length.
© EDP Sciences 2001