Ferroelectric switching and phase transitions in thin cells of chiral smectic liquid crystals

Fokin, Yu. G.; Krupenin, S.V.; Murzina, T. V.; Aktsipetrov, O.A.; Soria, Silvia; Marowsky, G.

doi:10.1016/j.susc.2004.06.012

Cited by 2 publications

(3 citation statements)

References 1 publication

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“…The term I 2,0 was added because SHG measurements in thin ferroelectric liquid crystal cells showed that such a term appears due to the "frozen" SmC * structure in contact with the substrates. 8,15,16 From Eq. ͑7͒ it follows that in the cells filled with hexadecane, the interference condition for two different SH contributions originating from the front ͑layer 1͒ and back ͑layer 2͒ walls of the cell is very important and for ⌬kL ϳ͓͑2N +1͔͒ can result in strong reduction of the net SHG signal.…”

Section: Discussionmentioning

confidence: 99%

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Ferroelectric switching of electrically commanded alignment layers for liquid crystal displays

Drevenšek‐Olenik

Kunstelj

Koncilija

et al. 2006

Journal of Applied Physics

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Optical second harmonic generation (SHG) was used to probe the structural and dynamic properties of electrically commanded alignment layers for liquid crystal displays. The layers were 200nm thick and were made of siloxane-based side chain ferroelectric liquid crystal polymer (FLCP). The effect of an external dc electric field in the range of 0–2V∕μm on the SHG signal was probed in an empty sandwich cell and in a cell filled with an isotropic liquid (hexadecane). In both cases the nonlinear induced polarization shows characteristics of the “V-shaped” switching, which is associated with a relatively minor reorientational perturbation of the film. This signifies a presence of domain structure, which is strongly pinned to the substrates. The values of switching times deduced from the SHG response are two orders of magnitude larger from the values obtained by optical birefringence measurements. This observation suggests that in the top surface layer of the FLCP, which is mainly responsible for the birefringence and also for the so-called electrically commanded surface effect, the reorientation of the polymer side chains takes place much faster than in the regions close to the substrate.

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Section: Discussionmentioning

confidence: 99%

“…The variable SHG signal in the SmA * phase can be explained by the electroclinic effect. 8,16 However, the origin of its unusual hysteresis is, for the moment, unclear and needs to be further investigated. Now we can make some comments on the observed differences between the SHG signal from the empty cell and the cell filled with hexadecane.…”

Section: Discussionmentioning

confidence: 99%

Ferroelectric switching of electrically commanded alignment layers for liquid crystal displays

Drevenšek‐Olenik

Kunstelj

Koncilija

et al. 2006

Journal of Applied Physics

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“…Critical exponents associated with phase transitions can be measured using SHG. Fokin et al (2004) measured the phase and switching characteristics of liquid crystals by monitoring the intensity of SHG signal transmitted by the liquid crystal cell. By changing the cell voltage and/or temperature a liquid crystal phase transition could be induced and the dynamics of the transition monitored.…”

Section: Second Harmonic Generation In Bulkmentioning

confidence: 99%

Characterization of the bulk properties of pharmaceutical solids using nonlinear optics - a review

Lee

Strachan

Manson

et al. 2007

Journal of Pharmacy and Pharmacology

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With the development of stable, compact and reliable pulsed laser sources the field of characterizing materials through their nonlinear optical response has bloomed. Second harmonic generation by non-centrosymmetric crystal structures has provided a new spectroscopic tool of potentially great utility in the pharmaceutical field. The nonlinear optical response of various materials provides a very sensitive technique for the characterization of pharmaceutically interesting bulk compounds and dispersions, and determining their concentrations. This work has potential application for in-line monitoring and quality control of pharmaceutical manufacturing. In this article we have presented an extensive review of the spectroscopic techniques that make use of the nonlinear optical response of solid media. Also, we have presented the results of our own work in this field.

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Ferroelectric switching and phase transitions in thin cells of chiral smectic liquid crystals

Cited by 2 publications

References 1 publication

Ferroelectric switching of electrically commanded alignment layers for liquid crystal displays

Ferroelectric switching of electrically commanded alignment layers for liquid crystal displays

Characterization of the bulk properties of pharmaceutical solids using nonlinear optics - a review

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