It is known that in uniformly oriented liquid crystal cells subject to uniform external electric field, pairs of topological defects of unitary topological charge of opposite sign appear spontaneously as result of symmetry breaking. They attract each other and annihilate to release the elastic constraint associated with director distortion around defects. Several techniques have been reported to date in order to control the location of generation of individual topological defects and their isolation from surrounding defects to secure their stability and provide large working area around the defect core. Here we will present our recent progress in controlled generation of self-engineered topological defects in vertically aligned nematic cells using structured electric and magnetic fields. In particular, we will report on ways to control their characteristics (e.g., spatial extent, core size, topology) in the context of developing advanced tunable liquid crystal diffractive waveplates for beam shaping and high-contrast imaging applications.
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