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Ultrafast Laser Physics and Precision Metrology Group

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Coherent Control


coh control
Spatial coherent control

We have developed a new method that combines spatial and spectral coherent control. Up to now most coherent control experiments have focused on spectral control, e.g. to steer energy transfer in molecules and atoms, optimize a two-photon transition, or control the dissociation or ionization of molecules.
However, these experiments were all based on a single excitation beam with shaped laser pulses. The possibilities for spatial control are then limited (to time focusing). Instead we use two counter-propagating beams with frequency comb pulses. This combination results in a very high spectral resolution with a strong suppression of Doppler-broadening, and at the same time allows to generate excitation patterns SPATIALLY. One of the surprising outcomes is that the total signal integrated over the whole interaction volume is independent of the phase pattern we put on the frequency comb pulses. In the paper mentioned below we show that complex pattern on a 10's of micrometer scale can be formed. We also show that different atomic species (Rubidium and Cesium) can be excited on a selected transition in different spatial positions, simply by adjusting the spectral phase of the laser pulses.
One application is the elimination of Doppler-broadened background in two-photon, direct frequency comb excitation. This leads to a much better signal-to-noise than without spatial coherent control, and therefore also to a significantly improved spectroscopic precision.
You can read more about in our Nature Photonics paper about it:

 
I. Barmes, S. Witte, K.S.E. Eikema,
Spatial and spectral coherent control with frequency combs
Nature Photonics 7, 38-42 (2013)
http://www.nature.com/nphoton/journal/v7/n1/pdf/nphoton.2012.299.pdf

See also the News and Views by A.M. Weiner on page 6-8 of the same issue: http://www.nature.com/nphoton/journal/v7/n1/pdf/nphoton.2012.334.pdf

Because the VU has no subscription to Nature Photonics, you might want to check out an earlier version of the paper on the arXiv: http://arxiv.org/abs/1207.5934





We gratefully acknowledge financial support from:
NWO FOM Laser Europe
VU fp 7 framework

Questions? Contact: k.s.e.eikema@vu.nl