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Q: Fachverband Quantenoptik und Photonik

Q 46: Ultrakurze Laserpulse (Erzeugung II / Anwendungen I)

Q 46.5: Vortrag

Donnerstag, 13. März 2008, 15:00–15:15, 3H

Octave wide tunable UV-pumped NOPA: pulse durations down to 20 fs and repetition rates up to 2 MHz — •Christian Homann, Christian Schriever, Peter Baum, and Eberhard Riedle — Lehrstuhl für BioMolekulare Optik, LMU München

For ultrafast spectroscopy, femtosecond laser pulses with wide tunability and high repetition rates are needed. Recently, amplified Yb-doped fiber systems became commercially available, delivering 10 μJ pulses at 1035 nm and 2 MHz repetition rate. We demonstrate frequency conversion with a noncollinear optical parametric amplifier (NOPA), which is pumped by the frequency tripled (345 nm) output of the fiber-amplifier system and is seeded by a smooth continuum generated in bulk sapphire. The 3ω light is generated with 15% conversion efficiency in a novel and extremely simple setup consisting of two BBO crystals only. The NOPA is tunable between 460 and 990 nm, thus spanning over one octave. The output pulses show smooth Gaussian shaped spectra and pedestal-free autocorrelation traces. Nearly Fourier-limited pulse durations down to 19.8 fs are achieved. The remaining green 2ω light from the frequency tripling setup is used to pump an additional, independently tunable NOPA with a tuning range of 600-970 nm. Together, the two NOPAs provide powerful sources for tunable two-color pump-probe spectroscopy. Interference experiments show that the two NOPA systems have a precisely locked relative phase, despite of being pumped by different harmonics with differing phase fluctuations. This directly proves that parametric amplification preserves the phase of the seed light.