Modelling the helical-flexo-electro-optic effect

The helical-flexo-electro-optic effect shows interesting in-plane electro-optic switching behaviour due to flexoelectric coupling with applied electric fields. Previous understanding of the behaviour has been generally based on an analytic approach which makes certain assumptions about the uniformity of the helical structure and the induced tilt angle under field application. Here we remove these assumptions and develop a perturbative approximation to describe the structure in more detail. We also use a numerical method to investigate the behaviour in regimes where the perturbative approach is inappropriate. The impact of variation in elastic constants and dielectric anisotropy is investigated. We find that dielectric behaviour in particular can lead to substantial differences between the tilt angle obtained here and those obtained using previous analytic models.