Ultra-high spatial resolutions in photopatterning molecular orientations

Accurately aligning liquid crystal molecules into predetermined spatially variant orientations is crucial for fabricating devices such as flat optical elements, soft actuators and robots. Despite the developments of various photopatterning techniques for this purpose, the limits of their spatial resolutions have been rarely addressed. In this study, we delve into the physical constraints governing the spatial resolutions of two prominent photopatterning methods: single exposure to light fields with structured polarizations and multi-exposures to light fields with structured intensities. Theoretical analyses show that the minimal grating period of the first method is only half of the Abbe limit of an intensity imaging system, and that the minimal grating period for the second system can surpass the Rayleigh limit. Experimental studies demonstrate unprecedent high spatial resolution with minimal grating periods of 1 µm. We further establish that the minimal core size in photopatterned singular topological defects is linearly proportional to the minimal grating period and the topological charge and that these photopatterning techniques can yield less than 1 µm defect cores that are in high demand for applications such as coronagraphs.