Düsseldorf 2007 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 19: Erzeugung ultrakurzer Lichtimpulse

Q 19.7: Vortrag

Dienstag, 20. März 2007, 12:00–12:15, 5K

Tunable pulses from below 300 to 950 nm with durations down to 12 fs from a 2 MHz Yb-doped fiber system — Christian Schriever, Patrizia Krok, •Stefan Lochbrunner, and Eberhard Riedle — Lehrstuhl für BioMolekulare Optik, LMU München

For many applications in spectroscopy, imaging, and machining, ultrafast low energy pulses at a high repetition rate are required. Fiber based femtosecond lasers are promising sources, however, they are not tunable which limits their application areas. We developed a noncollinearly phase matched optical parametric amplifier (NOPA) [1] for high repetition rates that not only provides the necessary tunability but also shortens the pulses by more than a factor of 10. A commercial 2 MHz Yb-doped fiber oscillator / fiber-amplifier system (IMPULSE; Clark-MXR, Inc.) delivering 10 µJ pulses at 1035 nm is used as pump. Its output is first frequency doubled, then the green is split off for pumping the NOPA stage while the remainder is used for continuum generation. The NOPA provides a tuning range of 600 - 950 nm with pulse energies up to 850 nJ. Due to the noncollinearity, the bandwidth can reach as much as 175 nm with a Fourier limit of 11 fs. With a fused silica prism sequence pulses at 865 nm were compressed to 11.9 fs and at 720 nm to 17.7 fs. Frequency doubling the NOPA output allows to access the spectral region of 300 - 475 nm and subsequent sum frequency mixing with NIR pump light reaches 233 - 326 nm. Applying these schemes, pulses at 427 nm were generated with an internal efficiency of 15% and pulses at 303 nm with 18% for the second step.

[1] T. Wilhelm, J. Piel, and E. Riedle, Opt. Lett. 22 1494, (1997).