References of "Nataf, Guillaume F."
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See detailHigh-contrast imaging of 180 degrees ferroelectric domains by optical microscopy using ferroelectric liquid crystals
Nataf, Guillaume F.; Guennou, Mael UL; Scalia, Giusy UL et al

in APPLIED PHYSICS LETTERS (2020), 116(21),

Ferroelectric liquid crystals (FLCs) couple the direction of their spontaneous electric polarization to the direction of tilt of their optic axis. Consequently, reversal of the electric polarization by an ... [more ▼]

Ferroelectric liquid crystals (FLCs) couple the direction of their spontaneous electric polarization to the direction of tilt of their optic axis. Consequently, reversal of the electric polarization by an electric field gives rise to an immediate and lasting optical response when an appropriately aligned FLC is observed between crossed polarizers, with one field direction yielding a dark image and the opposite direction yielding a bright image. Here, this peculiar electro-optic response is used to image, with high optical contrast, 180 degrees ferroelectric domains in a crystalline substrate of magnesium-doped lithium niobate. The lithium niobate substrate contains a few domains with upward electric polarization surrounded by regions with downward electric polarization. In contrast to a reference non-chiral liquid crystal that is unable to show ferroelectric behavior due to its high symmetry, the FLC, which is used as a thin film confined between the lithium niobate substrate and an inert aligning substrate, reveals ferroelectric domains as well as their boundaries, with strong black and white contrast. The results show that FLCs can be used for non-destructive readout of domains in underlying ferroelectrics, with potential applications in, e.g., photonic devices and non-volatile ferroelectric memories. [less ▲]

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See detailUltrafast acousto-optic mode conversion in optically birefringent ferroelectrics
Lejman, Mariusz; Vaudel, Gwenaelle; Infante, Ingrid C. et al

in Nature Communications (2016), 7

The ability to generate efficient giga-terahertz coherent acoustic phonons with femtosecond laser makes acousto-optics a promising candidate for ultrafast light processing, which faces electronic device ... [more ▼]

The ability to generate efficient giga-terahertz coherent acoustic phonons with femtosecond laser makes acousto-optics a promising candidate for ultrafast light processing, which faces electronic device limits intrinsic to complementary metal oxide semiconductor technology. Modern acousto-optic devices, including optical mode conversion process between ordinary and extraordinary light waves (and vice versa), remain limited to the megahertz range. Here, using coherent acoustic waves generated at tens of gigahertz frequency by a femtosecond laser pulse we reveal the mode conversion process and show its efficiency in ferroelectric materials such as BiFeO3 and LiNbO3. Further to the experimental evidence, we provide a complete theoretical support to this all-optical ultrafast mechanism mediated by acousto-optic interaction. By allowing the manipulation of light polarization with gigahertz coherent acoustic phonons, our results provide a novel route for the development of next-generation photonic-based devices and highlight new capabilities in using ferroelectrics in modern photonics. [less ▲]

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See detailEvolution of defect signatures at ferroelectric domain walls in Mg-doped LiNbO3
Nataf, Guillaume F.; Guennou, Mael UL; Haussmann, Alexander et al

in Physica Status Solidi. Rapid Research Letters (2016), 10(3), 222-226

The domain structure of uniaxial ferroelectric lithium niobate single crystals is investigated using Raman spectroscopy mapping. The influence of doping with magnesium and poling at room temperature is ... [more ▼]

The domain structure of uniaxial ferroelectric lithium niobate single crystals is investigated using Raman spectroscopy mapping. The influence of doping with magnesium and poling at room temperature is studied by analysing frequency shifts at domain walls and their variations with dopant concentration and annealing conditions. It is shown that defects are stabilized at domain walls and that changes in the defect structures with Mg concentration can be probed by the shift of Raman modes. We show that the signatures of polar defects in the bulk and at the domain walls differ. (C) 2016 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim [less ▲]

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See detailDirect observation of polar tweed in LaAlO3
Salje, Ekhard K. H.; Alexe, Marin; Kustov, Sergey et al

in SCIENTIFIC REPORTS (2016), 6

Polar tweed was discovered in mechanically stressed LaAlO3. Local patches of strained material (diameter ca. 5 mu m) form interwoven patterns seen in birefringence images, Piezo-Force Microscopy (PFM) and ... [more ▼]

Polar tweed was discovered in mechanically stressed LaAlO3. Local patches of strained material (diameter ca. 5 mu m) form interwoven patterns seen in birefringence images, Piezo-Force Microscopy (PFM) and Resonant Piezoelectric Spectroscopy (RPS). PFM and RPS observations prove unequivocally that electrical polarity exists inside the tweed patterns of LaAlO3. The local piezoelectric effect varies greatly within the tweed patterns and reaches magnitudes similar to quartz. The patterns were mapped by the shift of the E-g soft-mode frequency by Raman spectroscopy. [less ▲]

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