Berlin 2014 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 46: Ultrashort laser pulses II
Q 46.8: Talk
Thursday, March 20, 2014, 15:45–16:00, DO26 207
Realization of near-bandwidth-limited 7-fs Ti:Sapphire pulses at the foci of high-NA microscope objectives — •H. Wan1, S. Gomes da Costa1, H. B. de Aguiar1, G. Tempea2, and A. Volkmer1 — 13. Institute of Physics, Stuttgart ,Germany — 2FEMTOLASERS GmbH, Wien, Austria
We demonstrate that near-bandwidth-limited pulses with 7 fs durations and very clean temporal profile can be systematically achieved at the focus of commonly used, high-numerical-aperture microscope objectives. Controlling not only the group delay dispersion (GDD) but also the third-order dispersion (TOD) of the setup was of paramount importance for achieving these results. We coupled 6.4-fs laser pulses from a Ti:Sapphire oscillator into an inverted microscope, via an ultra-broadband dispersive mirror compressor that compensates both the GDD and TOD of the system. A pair of fused silica wedges was used for fine dispersion adjustment. The shortest pulse duration of 6.9 fs was achieved at the focus of an 20x NA 0.5 W objective. For a high-NA microscope objective (60x NA 1.2W), only slightly longer in-focus pulses of 7.1 fs are routinely attained. The efficiency of second harmonic and two-photon fluorescence excitation in nonlinear optical microscopies is predicted to increase linearly with decreasing pulse duration. This behavior has been previously demonstrated experimentally for pulse durations down to 20 fs only. Equipped with the setup described above, we first verified the validity of this prediction for pulses with durations down to 7 fs. These results pave the way for fundamental studies of ultrafast phenomena with sub-micron spatial resolution.