HIGH-ORDER HARMONIC-GENERATION BY SUBPICOSECOND KRF EXCIMER-LASER PULSES

We investigated the generation of high-order harmonics of a KrF excime r laser (80 mJ, 0.5 ps) in rare gases (He, Ne) and molecular gases (N- 2, O-2). The highest-order harmonic, 7.1 nm, the 35th, was observed in He and Ne, and 8.6 nm, the 29th, in N-2 and O-2. Our experimental res ults suggest that the high-order harmonics are emitted from ionized at oms. The maximum photon energy of the high-order harmonics may be rest ricted by phase mismatching caused by free electrons. (C) 1996 Optical Society of America