Vortex Induction via Anisotropy Stabilized Light-Matter Interaction

Abstract

By sending circularly polarized light beams onto a homeotropic nematic liquid crystal cell with a photosensitive wall, we are able to locally induce spontaneous matter vortices that remain, each, stable and trapped at the chosen location. We discuss the dual light-matter nature of the created vortices and demonstrate the ability of the system to create optical vortices with opposite topological charges that, consistent with angular momentum conservation, both derive from the same defect created in the liquid crystal texture. Theoretically, we identify a self-stabilizing mechanism for the matter vortex, which is provided by the concurrency of light-induced gradients and anisotropy of the elastic constants that characterize the deformation of the liquid crystal medium.

Light–matter interaction induces a single positive vortex with swirling arms

“…This approach provides both tunability and high efficiency, although the LC alignment can cause some beam deformation and a consequent degradation of the generated optical vortexes [21]. Recently, by exploiting reorientational nonlinearities in the nematic LC layer of a light valve, we have accomplished the optically addressed self-induction of vortex beams that are self-aligned with the impinging light beam [22]. The spontaneous nature of the induction process guarantees that the generated defect is aligned with the incoming light beam.…”

Manipulating the Orbital Angular Momentum of Light at the Micron Scale with Nematic Disclinations in a Liquid Crystal Film

“…In particular, the realization of micron-size spin-orbit optical vortex generators has been reported using nematic droplets [11]. However, so far, natural [11], electrical [12], optical [13,14], or electro-optical [15] strategies based on the spontaneous creation of defects all correspond to the case jsj ¼ 1. Following Eq.…”

Standing wave-mediated molecular reorientation and spontaneous formation of tunable, concentric defect arrays in liquid crystal cells

“…Interestingly, the director profile around the +1 defects has a concentric arrangement, that is, a vortex structure. 16 Although the +1 defects with radial director profiles are frequently found in LC cells, 13 the concentric director profiles are rarely observed. To reconfirm the director field structure, we examined the director profiles near the +1 and − 1 defects using two methods, an optical compensator technique and an FCPM analysis.…”

“…When linearly polarized light interferes with the donut-shape beam, a fork-shaped interference pattern with two dislocations appears, confirming an optical vortex with a topological charge of two (Figure 6c-ii). 16 Unique properties of the standing nematodynamic wave and asymmetric particle actuation The spontaneous standing wave and molecular rearrangement in the LC cell have several remarkable features that are different from those that characterize 2D-membrane films and rectangular cavities. 7,8 First, the pitch values of the periodic units depend on the frequency but not on the amplitude of the applied signals.…”

“…Additionally, tunable concentric defect arrays have not been achieved via another method. Well-controlled defects in LCs can serve as optical vortex inductors, [16][17][18][19][20] which have recently attracted attention for their fundamental properties and potential applications in quantum computational schemes and large data optical communication. 21,22 …”