Ferroelectric chiral nematic liquid crystals: new photonic materials with multiple bandgaps controllable by low electric fields

ABSTRACT

We have carried out a spectroscopic study on a prototype ferroelectric nematic material (RM734) doped with a non-polar chiral compound. The mixture presents two chiral nematic phases, one conventional (N*) and the other polar (N_F*), whose behaviours under electric fields E are totally different. On the one hand, the N* phase shows a single reflection band if E is not very high, while fields perpendicular to the helix of a few V/mm are already sufficient to produce multiple bands in the N_F* phase. On the other hand, the pitch of the N_F* phase grows notably on increasing fields, however remaining practically constant in the N* phase. Both effects have been explained in terms of the different type of interaction with E in each phase (ferroelectric in N_F* and dielectric in N*). We argue that the N_F* phase behaves as a photonic material with multiple gaps tunable by small fields, which presents important potentials for applications. A study of the bandgaps has been carried out through the analysis of the dispersion relation of the optical eigenmodes in the N_F* phase under field. Finally, an example of the potentials of the N_F* phase within the field of nonlinear optics is briefly presented.

GRAPHICAL ABSTRACT

KEYWORDS:

• Ferroelectric nematic phase
• chirality
• polar order parameter
• multiple gap photonic materials
• nonlinear optics

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Basque Government [project IT1458-22], the MICIU/AEI/FEDER, EU funds [project PGC2018-093761-B-C31] and the Gobierno de Aragón-FSE [E47-20R].