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Zusammenfassung:
The ability to manipulate ferroelectrics at ultrafast speeds has long been an elusive target for materials research. By using short optical pulses to coherently displace all atoms along the ferroelectric mode, witching times could be shortened by two orders of magnitude compared to what is possible with pulsed electric fields. Here, we report on the demonstration of ultrafast optical reversal of the ferroelectric polarization in LiNbO3. Rather than driving the ferroelectric mode directly, we couple to it indirectly by exciting an auxiliary high-frequency vibration. The ferroelectric polarization is then reversed due to the anharmonic coupling between the two modes, as revealed by time-resolved, phase-sensitive second-harmonic generation. Reversal can be induced in both directions, a key pre-requisite for practical applications.
