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Ultra-broadband two beam CARS using femtosecond laser pulses

: Matthäus, G.; Demmler, S.; Lebugle, M.; Küster, F.; Limpert, J.; Tünnermann, A.; Nolte, S.; Ackermann, R.


Vibrational spectroscopy 85 (2016), S.128-133
ISSN: 0924-2031
Fraunhofer IOF ()

Femtosecond (fs)-CARS is a promising approach for gas spectroscopy under high pressure and temperature conditions, as it allows probing molecular states on a time scale which is significantly shorter than the typical decay time induced by interfering collisions. Usually, fs-CARS is performed in a three beam setup, which requires maintaining spatial and temporal overlap of the pulses at the focal point. This is a challenging task, especially in harsh environments such as in a combustion chamber. In this study, we present an alternative approach, which uses two beams in a collinear configuration. An ultra-broadband, sub 7 fs laser pulse acts as pump and Stokes pulse, and a ∼500 fs pulse is used for probing. We show that this configuration is suitable for measuring the gas temperature and concentration. Furthermore, possible single shot measurements of the gas temperature are evaluated.