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Shaped pulses directly in the UV by an acousto-optic programmable dispersive filter
Now shaped ultrashort fs UV pulses are available. See paper at the bottom of the page.
Shaped UV pulses by chirped sum frequency mixing
Shaped and highly structured light pulses are successfully applied to control
atomic and molecular dynamics. To match the electronic absorption of organic
molecules they have to be in the ultraviolet. As liquid crystal spatial light
modulators (LC SLMs), are not available with high transmission in the UV, we
shape spectrally broad, tunable pulses in the visible with a LC SLM and transfer
them into the UV by SFM.
We extend the mixing scheme for the generation of shaped tunable ultrashort UV
pulses by strongly chirping and thereby stretching the NIR pulse.
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Advantages of chirped SFM |
- NIR pulses available from pump laser system
- high spectral resolution in the UV w/o reducing bandwidth and energy of the NIR pulses
- high conversion efficency of up to 25%
- broadband phase matching
- direct transfer of phase and amplitude
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Transfer of phase and spectral features
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The NIR mixing pulse is obtained by stretching
an almost Fourier limited Gaussian CPA pulse with a highly
dispersive SF57 glass block. It has two essential properties:
- it is quasi monochromatic on the 100 fs time scale
- its intensity is almost constant over several hundred femtoseconds
Describing the SFM process in time, the output pulse is the
product of the two input pulses and its phase is the sum of the phases of
the input pulses.
For strongly linearly chirped NIR pulses,
the linear chirp introduced by the NIR pulse is small
for short visible input pulses.
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Since complex pulse forms require complex, i.e. spectrally strongly modulated
mask functions, an important property of the setup is the linear
transfer of spectral features to the UV pulse. We have shown, that for a
sufficiently thin mixing crystal a modulated spectrum of more than 100 THz
bandwidth can be transfered without distortions into the UV.
We realised double and triple pulses with a total pulse separation of up
to 500 fs and a minimum structure duration of 20 fs.
We demonstrated pulse trains since they are particullarly well suited to
drive coherent vibrations in molecules. More complex arbitrary pulse shapes
can be generated just as easily due to the direct transfer of phase and amplitude
to the UV. By a simple realignment of the NOPA and the pulse shaper the full
spectral range from 295 to 370 nm is accessible.
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"Sub-20 fs pulses shaped directly in the UV by an
acousto-optic programmable dispersive filter"
N. Krebs, R. A. Probst, E. Riedle
Optics Express 18, 6164-6171 (2010)
Details
"19 femtosecond shaped ultraviolet pulses"
C. Schriever, S. Lochbrunner, M. Opitz, and E. Riedle
Opt. Lett. 31, 543 - 545 (2006)
Details
"Widely tunable sub-30 fs ultraviolet pulses by chirped sum frequency mixing"
Ida Z. Kozma, Peter Baum, Stefan Lochbrunner and Eberhard Riedle
Opt. Express 11, 3110 - 3115 (2003)
Details
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