Ferroelectrics and Non-linear Optics

Development of “smart” materials which properties can be manipulated by the external stimuli, is one of the paramount research areas in modern technology. In our lab, we are working on liquid crystals which optical properties (birefringence, direction of the optical axis) can be switched by the external electric field. A classical example of such materials is chiral SmC* phase. In thin glass cells this phase behaves as an improper ferroelectric. In phases of bent-core mesogens, the polar order does not necessarily require the chiral symmetry, and such compounds often behave as proper antiferroelectrics. In our research we study the switching behaviour and the Generation of the Second Harmonic (SHG) in compounds having a complex (ferro-/antiferro- and ferrielectric states) switching. Among our recent achievements is investigation of a multistage switching behaviour in bent-core smectics and studying of a quadratic “electroclinic” effect in the SmA and SmC phases of bent-core molecules.
Multistage switching in a polar smectic liquid crystals. The colours correspond to different magnitudes of birefringence.
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Field-induced tilt in a SmA phase of bent-core mesogens. The image is taken under crossed polarisers: field OFF

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Field ON


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