Fast Switchable Dual-Model Grating by Using Polymer-Stabilized Sphere Phase Liquid Crystal

Manipulation of sub-terahertz waves using digital coding metasurfaces based on liquid crystals

This paper presents a novel sub-terahertz liquid crystal (LC) phase shifter based on digital coding metasurfaces. The proposed structure consists of metal gratings and resonant structures. They are both immersed in LC. The metal gratings function as reflective surfaces for electromagnetic waves and electrodes for controlling the LC layer. The proposed structure changes the state of the phase shifter by switching the voltage on every grating. It allows the deflection of LC molecules within a subregion of the metasurface structure. Four switchable coding states of the phase shifter are obtained experimentally. The phase of the reflected wave varies by 0°, 102°, 166°, and 233° at 120 GHz. Due to the presence of the transverse control electric field, modulation speed is approximately doubled compared to the free relaxation state. This work provides a novel idea for wavefront modulation of phase.

Self-assembled liquid crystal architectures for soft matter photonics

Self-assembled architectures of soft matter have fascinated scientists for centuries due to their unique physical properties originated from controllable orientational and/or positional orders, and diverse optic and photonic applications. If one could know how to design, fabricate, and manipulate these optical microstructures in soft matter systems, such as liquid crystals (LCs), that would open new opportunities in both scientific research and practical applications, such as the interaction between light and soft matter, the intrinsic assembly of the topological patterns, and the multidimensional control of the light (polarization, phase, spatial distribution, propagation direction). Here, we summarize recent progresses in self-assembled optical architectures in typical thermotropic LCs and bio-based lyotropic LCs. After briefly introducing the basic definitions and properties of the materials, we present the manipulation schemes of various LC microstructures, especially the topological and topographic configurations. This work further illustrates external-stimuli-enabled dynamic controllability of self-assembled optical structures of these soft materials, and demonstrates several emerging applications. Lastly, we discuss the challenges and opportunities of these materials towards soft matter photonics, and envision future perspectives in this field.

Templated Twist Structure Liquid Crystals and Photonic Applications

Twist structure liquid crystals (TSLCs) have attracted increasing attention in photonic applications due to their distinct properties: Bragg reflection, scattering, and optical rotation. However, there exist some issues due to the defects of TSLCs: weak thermal stability, narrow bandwidth, and complicated fabrication. In this review, we introduce the templating technique which includes device structure, templating process, and photonic properties of templated TSLCs to improve the issues. Furthermore, a variety of photonic applications including lasing, optical filters and gratings based on TSLCs with polymer templates are presented. Additionally, other applications of TSLCs are briefly introduced. Finally, the remaining challenges and future perspectives of templated TSLCs are proposed.

Dynamic Control of Light Direction Enabled by Stimuli-Responsive Liquid Crystal Gratings

The ability to control light direction with tailored precision via facile means is long-desired in science and industry. With the advances in optics, a periodic structure called diffraction grating gains prominence and renders a more flexible control over light propagation when compared to prisms. Today, diffraction gratings are common components in wavelength division multiplexing devices, monochromators, lasers, spectrometers, media storage, beam steering, and many other applications. Next-generation optical devices, however, demand nonmechanical, full and remote control, besides generating higher than 1D diffraction patterns with as few optical elements as possible. Liquid crystals (LCs) are great candidates for light control since they can form various patterns under different stimuli, including periodic structures capable of behaving as diffraction gratings. The characteristics of such gratings depend on several physical properties of the LCs such as film thickness, periodicity, and molecular orientation, all resulting from the internal constraints of the sample, and all of these are easily controllable. In this review, the authors summarize the research and development on stimuli-controllable diffraction gratings and beam steering using LCs as the active optical materials. Dynamic gratings fabricated by applying external field forces or surface treatments and made of chiral and nonchiral LCs with and without polymer networks are described. LC gratings capable of switching under external stimuli such as light, electric and magnetic fields, heat, and chemical composition are discussed. The focus is on the materials, designs, applications, and future prospects of diffraction gratings using LC materials as active layers.