The flexoelectro-optic effect in cholesterics

被引:42
作者
Rudquist, P
Carlsson, T
Komitov, L
Lagerwall, ST
机构
[1] Chalmers University of Technology, Göteborg
关键词
D O I
10.1080/026782997209153
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
The flexoelectro-optic effect in short-pitch cholesterics [1] is analysed in terms of applied electric field strengths and material parameters such as the two flexoelectric coefficients e(s) and e(b) and the three elastic constants. Starting from the free energy density of the uniformly lying-helix (ULH) configuration, including the flexoelectric polarization term, the equation describing the field-induced tilt angle of the bulk optic axis is derived. It is convenient to introduce the flexoelectric 'anisotropy' Delta e as the difference between the splay and bend flexoelectric coefficients, hence defined by Delta e = e(s) - e(b). Our results then show that Delta e is the essential material parameter controlling the sign and magnitude of the electrically induced tilt. In the region of linear approximation, the tilt is proportional to Delta e and to the electric field E, and inversely proportional to the helical wave vector It, as well as the effective elastic constant (K-11 + K-33). The individual values of the elastic constants K-11, K-22 and K-33 do have an influence on the magnitude of the effect, but not on its linearity. The Delta e dependence conforms in the simplest way to the physical requirement that the flexoelectro-optic effect must be particularly pronounced in the case that e(s) and e(b) are of opposite sign.
引用
收藏
页码:445 / 449
页数:5
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