Femtosecond vacuum-ultraviolet pulse measurement by field-ionization dynamics

Generation of tunable sub-45 femtosecond pulses by noncollinear four-wave mixing

Generation of sub-45 fs vacuum UV (VUV) pulses tunable across the spectral range of 146-151 nm at 1 kHz repetition rate is reported. The pulses are produced using noncollinear difference-frequency four-wave mixing between the third-harmonic of an amplified Ti:sapphire laser and the signal wavelength of an infrared optical parametric amplifier (ω(VUV)=2ω(TH)-ω(IR)) in krypton and argon. The generated VUV pulses have energies as high as 90 nJ. Pulse duration measurements are realized by cross correlation between the VUV pulses and the laser fundamental wavelength using pump-probe ionization in xenon.

Femtosecond measurement of high-order harmonic pulse width and electron recombination time by field ionization

We measured the ultrashort XUV pulse width by the pump-probe method, using femtosecond dynamics of field ionization. We measured the pulse width of the ninth harmonic (88.3 nm) of a Ti:sapphire laser, using the difference of the absorption cross section between Kr and Kr(+). The change of transmission of the ninth harmonic for the delay between the pump and the probe pulses gives both the pulse width of the ninth harmonic and the recombination time of Kr(+). The measured pulse width of the ninth harmonic was 260 fs. The recombination time of Kr(+) was ~2 ps, which does not contradict the estimated time of the threebody recombination.

Generation of high-power subpicosecond pulses at 155 nm

Subpicosecond vacuum-ultraviolet radiation at 155 nm with pulse energies above 0.2 mJ has been obtained by near-resonant four-wave difference-frequency mixing in a Xe gas jet. Laser fields for the mixing process have been generated by a short-pulse KrF dye excimer laser system and a Raman converter. The process permits tuning in a broad vacuum-ultraviolet range and can be scaled up to higher output energies.