The effect of electric fields on blue phase III with negative dielectric anisotropy

In order to further understand the structure of the blue phase III (BPIII) phase of chiral liquid crystals, we have observed the effect of electric fields on the reflectivity of BPIII phases in which the liquid crystal has negative dielectric anisotropy. The reflectivity increases dramatically with increasing field, in contrast to the behaviour for materials of positive dielectric anisotropy. We compare the data with cubic domain and double-twist models for BPIII structure and we find that the data best agree with the double-twist model and possibly with an O5 cubic domain model.