We employ GaS0.4Se0.6 nonlinear crystal for difference-frequency generation between signal and idler of a synchronously pumped femtosecond OPO at 80 MHz achieving continuous tuning from 4 μm (>12 mW) to 12 μm (>0.5 mW).

We report the generation of sub 20 fs UV pulses with 300 μJ energy at 1 kHz repetition rate by applying spectral broadening of the UV pulses during filamentation in argon.

Here we present the shortening of the VUV pulses to less than 20 fs by the application of sub-15-fs idler pulses provided by the use of nonlinear spectral broadening of the FF pulses during filamentation. The pump laser provides up to 3 mJ pulses at 800 nm with 40 fs duration. Using a 1:1 beam splitter (BS), 50% of the pulse energy is applied for spectral broadening in an argon filled gas cell at a pressure of 1.1 bar. After spectral broadening, the FF pulses are compressed to less then 15 fs using chirped mirrors.

Using the efficient nonlinear conversion scheme which was recently developed in our group [M. Beutler, M. Ghotbi, F. Noack, and I. V. Hertel, Opt. Lett. 134, 1491 (2010); M. Ghotbi, M. Beutler, and F. Noack, ibid 35, 3492 (2010)] to provide intense sub-50 fs vacuum ultraviolet laser pulses we have performed the first real time study of ultrafast, photo-induced dynamics in the electronically excited Ã-state of water clusters (H(2)O)(n) and (D(2)O)(n) , n=2-10. Three relevant time scales, 1.8-2.5, 10-30, and 50-150 fs, can be distinguished which-guided by the available theoretical results-are attributed to H (D)-ejection, OH (OD) dissociation, and a nonadiabatic transition through a conical intersection, respectively. While a direct quantitative comparison is only very preliminary, the present results provide a crucial test for future modeling of excited state dynamics in water clusters, and should help to unravel some of the many still unresolved puzzles about water.

Generation of sub-50fs vacuum UV pulses with more than 2.5μJ energy at a 1kHz repetition rate is reported. The pulses at 160nm are produced using noncollinear difference-frequency four-wave mixing between the fundamental and third harmonics of an amplified Ti:sapphire laser in argon. While the pulse duration is maintained by increasing the phase-matching pressure, noncollinear interaction improves the conversion efficiency by 1 order of magnitude in comparison with the previous results in collinear geometry.

We report efficient generation of tunable femtosecond pulses in the near IR using a two stage, white-light seeded, collinear, femtosecond optical parametric amplifier (OPA). The OPA, based on BiB(3)O(6) crystal in both stages and pumped at 807 nm by a 1 kHz Ti:sapphire laser amplifier, provides sub-30 fs signal pulses after compression with energies exceeding 200 microJ, which corresponds to fivefold pulse shortening and approximately 30% internal conversion efficiency in the second stage considering 150 fs pump pulses with 1.5 mJ energy. The corresponding idler pulses with more than 100 microJ have sub-60 fs duration without compression. The first stage alone is capable of producing sub-20 fs pulses near 1400 nm at the microjoule level without using any compression.

We report efficient generation of high energy femtosecond pulses in the near-IR using a two stage, white-light seeded femtosecond optical parametric amplifier (OPA). The OPA, based on two 3-mm crystals of BiB3O6 and pumped at 807 nm by a 1 kHz Ti:sapphire laser amplifier can provide femtosecond signal pulses over the 1150-1450 nm range. Frequency resolved optical gating measurements result in near-transform-limited pulses with durations down to 27-fs for 200-fs pump pulses corresponding to more than 7 times pulse shortening.