Seminars Archive

Degenerate Four-Wave Mixing with ultrashort pulses.

Abstract
In the first part of the talk, the Four-Wave Mixing FWM experiments with sub 20 fs pulses will be presented. The FWM technique in time domain enables excitation and observarion of the vibrational wavepackets on the electronic ground and excited state. Moreover, we show that pump-DFWM in combination with spectral detection can be applied to the study of complex molecular systems, where optically dark electronic states are common [1]. The coherent control in an open loop with liquid crystal phase mask is demonstrated in all-trans-beta carotene. The difference between resonant and non-resonant case clearly shows enhancement of Raman modes in the resonant case [2]. The second part of the talk, deals with the modified Direct Freequency Comb Spectroscopy (DFCS) which utilizes a fixed frequency comb spectrum and an additional cw scanning probe laser. We have shown that resonant excitation of the rubidium atoms by discrete frequency comb optical spectrum results in the comblike velocity distribution of the excited state hyperfine level populations and velocity selective population transfer between the Rb ground state hyperfine levels. [3, 4]. The recent work in our group shows that accumulation of population and coherence, as direct results of the frequency comb excitation, can be effectively reduced and eventually destroyed by increasing the cw probe laser intensity [5]. A strong cw laser can therefore serve as a switch from the pulse-train (i.e. frequency comb) to pulse-by-pulse type of interaction of Rb atoms with the fs laser. [1] T. Hornung, H. Skenderović, and M. Motzkus, Chem. Phys. Lett. 402 283 (2005). [2] J. Hauer, H. Skenderović, K-L. Kompa, and M. Motzkus, Chem. Phys. Lett. 421 523 (2006). [3] D. Aumiler, T. Ban, H. Skenderović, and G. Pichler, Phys. Rev. Lett. 95, 233001 (2005). [4] T. Ban, D. Aumiler, H. Skenderović, and G. Pichler, Phys. Rev. A 73, 043407 (2006). [5] T. Ban, D. Aumiler, H. Skenderović, S. Vdović, N. VujiĿić, and G. Pichler, Phys. Rev. A 76, 43410 (2007).