Hamburg 2009 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 14: Ultrakurze Pulse: Erzeugung II

Q 14.6: Talk

Monday, March 2, 2009, 17:45–18:00, VMP 8 R206

Infrared generation beyond BBO: easy tuning from 850 nm to above 5 μm with novel optical parametric amplifiers — •Maximilian Bradler, Christian Homann, Markus Breuer, and Eberhard Riedle — LS für BioMolekulare Optik, LMU München

Ultrashort few-cycle pulses in the Mid-Infrared (MIR) are interesting for many applications such as time-resolved vibrational spectroscopy or high-field science. The most common approach to produce tunable MIR pulses is difference frequency mixing, e.g. of the signal and idler of an optical parametric amplifier (OPA). However, this renders a relatively narrow bandwidth, pulse lengths not much below 100 fs and low overall conversion efficiency in the 1 % range. Here we present a hybrid approach that yields ultrashort carrier-envelope-phase stable MIR pulses up to 5 μm directly as the output of an OPA. We first preamplify selected parts of a white-light supercontinuum generated in yttrium aluminum garnet (YAG) in BBO. As pump we use the second harmonic of a Ti:Sa regenerative amplifier for tunability in the wavelength range between 850 nm and 1550 nm. In a second stage we further amplify these pulses in a LiNbO3 crystal pumped by the 775 nm fundamental output of the Ti:Sa laser. This directly renders idler pulses in the desired wavelength range from 1550 nm to about 5.3 μm. With 240 μJ total pump energy we achieve pulse energies of more than 5 μJ up to 4 μm corresponding to an overall efficiency of more than 8% over a wide tuning range. The transform limit of the pulse widths is as low as 25 fs. An autocorrelation measurement confirms a pulse width of 42 fs at 3.8 μm, equivalent to just 3.5 optical cycles.