Spatially twisted liquid-crystal devices

Nematic liquid-crystal devices are a powerful tool to structure light in different degrees of freedom, both in classical and in quantum regimes. Most of these devices exploit the possibility of introducing a position-dependent phase retardation either with a homogeneous alignment of the optic axis-e.g., liquid-crystal-based spatial light modulators-or, conversely, with a uniform but tunable retardation and patterned optic axis, e.g., q-plates. The pattern is the same in the latter case on the two alignment layers. Here, a more general case is considered, wherein the front and back alignment layers are patterned differently. This creates a non-symmetric device, which can exhibit different behaviors depending on the direction of beam propagation and effective phase retardation. In particular, we fabricate multi-q-plates by setting different topological charges on the two alignment layers. The devices have been characterized by spatially resolved Stokes polarimetry, with and without applied electric voltage, demonstrating new functionalities. (c) 2024 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license(https://creativecommons.org/licenses/by/4.0/).