Grandjean-Cano disclinations

Figure 9. Typical Cano-wedge textures for a chiral nematic. The Grandjean-Cano disclination lines occur at the blue-yellow interface. The slightly curved distortion shows how sensitive the technique is to undulations in the glass of the wedge cell used here.

A special case was considered in [21]. The dielectric instability was investigated in the hybrid [4] or so-called corkscrew texture. A wedge-form cell was prepared with the planar and homeotropic orientation of a cholesteric mixture at opposite boundaries. It was shown that the Cano-Grandjean disclinations are not observed in this case and the electrooptical response... 

To obtain the pitch value we can use the Cano-Grandjean texture in a wedge-shaped cell having the helical axis perpendicular to the substrates. In this case, Rq is equal to double the distance between two neighboring disclinations [23, 44]. Rq could also be defined by measuring the positions of the optical Bragg reflection maxima, if the refractive indices are known... 

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