A self-healing ferroelectric liquid crystal electro-optic shutter based on vertical surface-relief grating alignment

Peter J M Wyatt,Mamatha Nagaraj,James Bailey,J Cliff Jones

doi:10.1038/s41467-021-24953-5

Peter J M Wyatt, Mamatha Nagaraj + Show 2 more

Open Access

https://doi.org/10.1038/s41467-021-24953-5

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Journal: Nature Communications	Publication Date: Aug 5, 2021
Citations: 15	License type: open-access

Affiliation: University of Leeds

Abstract

Ferroelectric liquid crystals remain of interest for display and spatial light modulators because they exhibit significantly faster optical response times than nematics. However, smectic layers are sensitive to shock-induced flow and are usually permanently displaced once a well-aligned sample is disrupted, rendering such devices inoperable. We introduce a vertical alignment geometry combined with a surface-relief grating to control both the smectic layer and director orientations. This mode undergoes “self-healing” of the smectic layers after disruption by shock-induced flow. Sub-millisecond switching between optically distinct states is demonstrated using in-plane electric fields. Self-healing occurs within a second after being disrupted by shock, wherein both the layer and director realign without additional external stimulus. The route to material improvements for optimised devices is discussed, promising faster spatial light modulators for high-speed adaptive optics, micro-displays for virtual/augmented reality and telecommunications with inherent shock stability.

Highlights

Ferroelectric liquid crystals remain of interest for display and spatial light modulators because they exhibit significantly faster optical response times than nematics
A simple geometry for Ferroelectric liquid crystals (FLCs) electrooptic shutters is presented in Fig. 1a–e, based on sub-micron amplitude and micron-scale pitch surface-relief gratings
The surface-relief gratings are embossed[28,31] into a photopolymer on top ITO in-plane switching (IPS) electrodes on one substrate, and on to plane glass on the opposing substrate, given the appropriate spacing using plastic beads in the conventional fashion, and capillary filled with the FLC material in its nematic phase

Summary

Introduction

Ferroelectric liquid crystals remain of interest for display and spatial light modulators because they exhibit significantly faster optical response times than nematics. FLCs in such devices are susceptible to shock, whereby induced viscous flow disrupts the well-aligned smectic layers causing optically visible damage that is effectively permanent[7,8] This weakness made FLC unsuited for large area displays. Liquid-Crystal-on-Silicon (LCoS) spatial light modulators based on FLC are commercially successful[9,10,11,12], and are less sensitive to shock, shock-insensitive modes remain important to explore and develop for the generation of portable and wearable devices They must exhibit ultra-high resolution, be light weight with a low power consumption, whilst demonstrating high diffraction or transmission efficiencies[13]. More complex geometries of surfacerelief gratings for nematic liquid crystals have seen commercial success with the zenithal bistable display (ZBD)[25], where deep homeotropic surface-relief gratings are implemented to induce surface bistability in a TN display[26,27], whilst only introducing one additional fabrication step, namely, introducing the surfacerelief gratings to the manufacturing process[28]

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