FEMTOSECOND EXTREME-ULTRAVIOLET QUASI-CONTINUUM GENERATION BY AN INTENSE FEMTOSECOND TI-SAPPHIRE LASER

A femtosecond broadband extreme-ultraviolet quasi-continuum was genera ted by an intense femtosecond Ti:sapphire laser by two nonlinear optic al processes. The first process is the generation of the broadband har monics by focusing the blueshifted laser pulse through a rare gas. The spectral blueshift is caused by self-phase modulation owing to ioniza tion of the target gas. The second process is the generation of broadb and even-order harmonics by the superposition of the second-harmonic e lectric field upon the fundamental. (C) 1998 Optical Society of Americ a.