engleski

Coherent Control by Four-Wave Mixing

The primary goal of coherent control is to drive a quantum system to the desired final state acting on the system with laser field(s). In the transient grating fs degenerate four-wave mixing (DFWM) scheme the pump and dump laser beams simultaneously populate several Raman levels. The signal is obtained by probing the coherence with the third pulse set at different time delays after the first two pulses. Control is achieved by shaping the pump and dump pulses with a periodic spectral phase which generates the pulse train of equally spaced pulses in time. Two different colors are used for the control the ground-state high-frequency vibrational modes (1000 - 1500 cm-1) of the all-trans ß-carotene dissolved in cyclohexane. The selective excitation of a desired mode is achieved in the non-resonant case. In addition to the mode selectivity, the mode enhancement is achieved in the resonant case, i.e. when the laser frequency was resonant with an electronic transition between the ground and the first excited state.

Four Wave mixing; coherent control

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