Precise control of the surface topographies of polymer materials is key to developing high-performance materials and devices for a wide variety of applications, such as optical displays, micro/nanofabrication, photonic devices, and microscale actuators. In particular, photocontrolled polymer surfaces, such as photoinduced surface relief, have been extensively studied mainly through photochemical mass transport. In this study, we propose a novel method triggering the mass transport by photopolymerization of liquid crystals with structured light and demonstrate the direct formation of microscale well and canal structures on the surface of polymer films. The wells and canals with depths of several micrometers and high aspect ratios, which are 10 times larger than those of previously reported structures, were found to be aligned in the center of non-irradiated areas. Furthermore, such well and canal structures can be arranged in two dimensions by designing light patterns. Real-time observations of canal structure formation reveal that anisotropic molecular diffusion during photopolymerization leads to a directed molecular alignment and subsequent surface structure formation.

The overall performance of liquid crystal devices is determined by a large number of interlinked features. We demonstrate that an easy-to-implement methodology and optical technique can provide a comprehensive characterisation and mapping of liquid crystal systems, capturing their static as well as dynamic properties. It has also been successfully applied to thin liquid crystal cells, planar and twisted cells. The technique is not only a powerful tool for optimising the choice of materials for each specific application, but also offers a great insight in the polarisation dynamics of light propagating in the anisotropic and multi-layer liquid crystal systems.

The increasing demand from large-scale high-density sensing arrays also raises new requirements for sensors such as higher sensitivity, more comprehensive response range but lower cost, smaller size, etc. For example, in large-scale structure health monitoring, [1-3] a sensing array can significantly decrease the cost and effort of manpower and provide a real-time and precise diagnosis of buildings. However, the power supply of the sensing probe is a vital problem to be solved: the maintenance of batteries or energy harvesters for such a large number of sensors is a considerable challenge. Besides, the low cost of sensing array is the foundation of a large-scale high-density sensing network. When we deploy these sensors below the ground or on the seabed, the problem becomes multi-fold complicated. A passive sensing technique can be a perfect solution, which needs no additional power during energy transduction. The power supply and signal process components are removed from the passive sensing probe. Thus, the cost of the sensing array can be significantly dropped while the structural complexity is reduced, and the lifetime can be much longer. [4]

This paper demonstrates simulations of the polarization gratings and switchable liquid crystal waveplates that give rise to a beam-steering method for liquid crystal lasers. This method does not involve any change in the configuration of the helical structure, nor does it result in an alteration of the laser wavelength. It also has a minimal impact on the intensity of the laser emission. Besides, the polarization state distribution of a band-edge liquid crystal laser has been investigated based on Stokes parameters measurements. The polarization profile of the liquid crystal laser serves as input for beam-steering simulation, with the result revealing consistency with the measured intensities of polarization grating diffraction spots.

Two-photon direct laser writing (TPP-DLW) in liquid crystals (LCs) enables a wide range of novel stimuli-responsive functionalities to be realised, which are potentially of interest for a range of technologies such as augmented reality (AR) / virtual reality (VR) displays, optical beamsteering, fast-switching devices and much more. In this presentation, we will demonstrate a method of fabricating mechanically deformable anisotropic films that behave as tunable diffraction gratings. These stretchable diffraction gratings have been fabricated using a combination of TPP-DLW and UV polymerization. For the fabrication of the grating, the LC director is frozen-in periodically to form alternating regions of high and low refractive index. To obtain the low and high refractive index, the LC director is locked-in at two different applied voltages to control the orientation of the director at the moment of exposure to the light source. When the free-standing films are subsequently subjected to a mechanical stress in the plane of the grating, it is found that there is a change in the grating period when observed on a polarizing optical microscope, which results in a concomitant change in the far-field diffraction pattern. Finally, our experimental findings for the diffraction intensity of the different orders in the far-field pattern are compared with predictions from simulations.

An electrically tunable progressive lens based on a liquid crystals(LC) is investigated and demonstrated. The proposed progressive LC lens could be a positive or a negative lens with a continuously tunable focal length. The progressive LC lens shows the spatially distribution in lens power ranging from +4D to -4D even though the lens power of the LC lens seems only -0.87D ~ +0.87 D calculated under parabolic wavefront approximation. The surprising results we present in this paper give LC lenses an insightful aspect and overrule the traditional statement of the limitation of lens power set by the optical phase difference in gradient-index LC lenses. It also paves a way in ophthalmic applications.

With the growing awareness of the impact of climate change and the need to conserve energy, smart window technologies have emerged as a promising solution. Liquid crystal/polymer composites-based switchable windows, such as PDLC, PSLC, and PSCT, offer the ability to regulate both privacy and radiant energy flow. In this study, we investigated the potential of these windows and identified methods to enhance their capabilities. Our results indicate that PDLC and PSCT windows with the appropriate film thickness have the potential to control radiant energy flow, while also providing improved privacy and comfort for building occupants.

In this work, we developed a photoalignment and photopatterning method to fabricate polymer-stabilized-liquid-crystals (PSLCs) for optical data encryption and anti-counterfeiting purposes. The PSLCs possess both implicit optical patterns as well as explicit geometries, could serve with improved environmental robustness and thermal stability after a post-extraction process, and can be directly bonded onto various substrates. Based on this, we prototyped proof-of-concept optical data encryption and anti-counterfeiting demonstrations using either one single photoaligned and photopatterned PSLC, or a pair of cascade, spatially programmed PSLCs.

The adoption of light emitting diodes by lighting industry is inevitable. They provide many advantages, but one of them is very interesting from the point of view of using liquid crystals: it is the small etendue of these sources. Rather well collimated and small diameter white light beams can be obtained. Here is where liquid crystal lenses can have an important application. We report the development of an optical element that can dynamically stretch broad band beams in one or in orthogonal or in both directions. Thus, we can start from a narrow circular beam and obtain a rectangular shaped beam to fit perfectly the size and the exposure requirements in home, office, architectural or automobile applications. The basics of its operation as well as of its optical performance data will be reported.

All-dielectric metasurfaces have exceptional potential for next-generation tunable optical systems, which are promising for applications in sensing, ranging, and imaging. One attractive way to achieve tunability is by infiltrating dielectric metasurfaces with liquid crystals due to the large tunability that can be achieved. Here, we introduce a fully controllable 3D active tuning of dielectric metasurfaces that include liquid crystals, where an external magnetic field effectively controls molecular reorientation. This approach offers new opportunities for realizing dynamically reconfigurable metadevices without the usual limitations imposed by fixed boundary conditions induced by molecular pre-alignment, which cannot be changed.

The cholesteric liquid crystalline (CLC) phase self-organizes into a periodic structure and in the planar orientation, exhibits a selective reflection. These materials are widely considered for applications in optics and photonics, including emerging applications in immersive displays. Polymerization of a small concentration of monomer can stabilize the CLC phase (polymer stabilized CLC, or PSCLC). We have recently been exploring an ion-mediated mechanism to displace the polymer stabilizing network. It is well known that liquid crystal mixtures retain ions such as Na+, NH4+, K+, Mg2+, Ca2+, Zn2+, and Al3+. These ions can negatively impact the performance of liquid crystal devices (response time, image sticking, color staining, and voltage holding ratio). However, these impurities can be leveraged in this mechanism. Accordingly, this presentation reports that the preparation of polymer stabilizing networks with rational incorporation of ion-trapping groups, such as 4-acryloxyterpyridine (TPy-Ac), 4-((6-(Acryloyl)oxy)benzoic-15-crown-5-ether (OBA-15C5), and 4-((6-(Acryloyl)oxy)benzoic-18-crown-6-ether (OBA-18C6). The polar nature of these comonomers can capture transition and alkali metal ions. This presentation will detail the ion-material coupling and the resulting impact on electro-optic performance.

Liquid crystals are widely known for their technological uses in displays, electro-optics, photonics and nonlinear optics, but these applications typically rely on defining and switching non-topological spatial patterns of the optical axis. Here, we demonstrate how a liquid crystal’s optical axis patterns with singular vortex lines can robustly steer beams of light. External stimuli, including an electric field and light itself, allow us to reconfigure these unusual light–matter interactions. Periodic arrays of vortices obtained by photo-patterning enable the vortex-mediated fission of optical solitons, yielding their lightning-like propagation patterns. Predesigned patterns and spatial trajectories of vortex lines in high-birefringence liquid crystals can steer light into closed loops or even knots. Our vortex lattices might find technological uses in beam steering, telecommunications, virtual reality implementations and anticounterfeiting, as well as possibly offering a model system for probing the interaction of light with defects, including the theoretically predicted, imagination-capturing light-steering action of cosmic strings, elusive defects in cosmology.

Spatial branching processes are ubiquitous in nature, yet the mechanisms that drive their growth may vary significantly from one system to another. In soft matter physics, chiral nematic liquid crystals provide a playground to study the emergence of disordered branching patterns in a controlled setting. Via an appropriate forcing, a cholesteric phase may nucleate in a chiral nematic liquid crystal, which self-organizes into an extended branching pattern. It is known that branching events occur when the rounded tips of cholesteric fingers swell, become unstable, and split into two new cholesteric tips. The origin of this interfacial instability and the mechanisms that drive the large-scale spatial organization of these cholesteric patterns remain unclear. In this work, we investigate the spatial and temporal organization of thermally-driven branching patterns in chiral nematic liquid crystal cells experimentally. We describe the observations through a mean-field model and find that chirality is responsible for the creation of fingers, regulates their interactions, and controls the tip-splitting process. Furthermore, we show that the complex dynamics of the cholesteric pattern may be reduced to a small set of interaction rules that drive the large-scale morphological and topological organization. Our theoretical findings have a good agreement with the experimental observations.

Chiral liquid crystal phases are fascinating materials with unique optical and structural properties that make them attractive for various technological applications. Understanding the mechanisms behind their structure transformation, deformation, and optical properties is crucial for their successful implementation in devices. Moreover, creating a mono-domain blue-phase liquid crystal is of great interest due to its potential for high-speed display applications. In this talk, I would like to introduce LC phases with periodic helical structures, induced by adding chiral molecules into the nematic phase. By changing the chirality and temperature, we can obtain one-dimensional and three-dimensional periodic helical structures. When the periodic helical structures and the wavelength of the incident light are satisfied with Braggs' reflection condition, the helical LCs reflect various visible colors. The attractive thing is that the reflection and of them can be tunable in many ways easily. For 3-D helical LC, called blue-phase liquid crystal, the tunable reflection band comes from the lattice deformation and matainsites transformation, checked by lattice diffraction.

Photovoltaic spatial light modulators combine liquid crystals with organic photovoltaic layers to achieve self-activated transmittance modulation. Short response times, energy-efficient operation, and user-controllable sensitivity make these devices attractive for many applications. We will show that the transmittance modulation is highly reversible and can be stable for hours under light exposure. Modulators based on new organic materials, selected to enhance the transmittance of the clear state and device sensitivity, will be presented. Results illustrating selective transmittance modulation in the near-infrared to control solar heating, while harvesting near-UV light will be shown. Remaining challenges and development possibilities will be outlined.

Here we will show the methodology to prepare multiple topological defects in a microfluidic device. The topological defects were stabilized by optimizing the size and shape and satisfying the boundary conditions inside each micro-well. Furthermore, we introduced the liquid on liquid crystals by modifying the microfluidic device. The introduction of various liquidscould show a variety of alignments for the liquid crystals, which could provide topological defects in a well. When the photo-responsive molecules at the interfaces could control the on/off behavior of the topological defects. This is a new platform for studying the properties of topological defects and their functions.

Ferroelectric nematic liquid crystal (NF) is a novel state of matter discovered in very recent years, that exhibits simultaneously high fluidity and ferroelectricity. The polar nature of its order parameter has significant impact on topological defects. Combined with designable photopatterned alignment, various electric polarization topologies beyond solid ferroelectric materials are expected to be achieved and controlled in NF, leading to promising research value in condensed matter physics and electro-optical devices. Here, we investigated the NF phase under confinement of flat surfaces with patterned director of topological defects. These director patterns based on azo-dyes are non-polar for the NF. Our results show that the polar orientation orders of NF including the polar domains and the layout of domain walls are significantly affected by the designed patterns and the confinements. Domain walls could follow the local orientation and emerge with relatively regular arrangements. Different polarization topologies can be observed around defect’s core, and be tuned by surface confinement and defects design. These structures are consequences of electrostatics, elastic energy, surface anchoring, and confinement. Our research could inspire the design and construction of the polar orientation orders in NF.

Systems with energy injection and dissipation self-organise by forming patterns of stripes, hexagons, squares, and superlattices at the onset of spatial instabilities. Increasing the disproportion between injection and dissipation of energy generates the emergence of disordered patterns with complex spatiotemporal behaviours. We investigate the turbulent dynamics of labyrinthine patterns far from the primary spatial instabilities in a liquid crystal light valve with optical feedback experiment. The structure functions associated with light intensity allow us to establish that the observed dynamical behaviours are also of intermittent nature.