Structural formation process in a cylindrical cholesteric droplet with air interface was observed and analyzed. A specific control of temperature change process enabled us to switch the final structure obtained as a result of the formation, via reconnection of loop defects in the transient state during the structure formation. Simultaneously, the existence of the gradient resulted in the characteristic rotational phenomenon called Lehmann rotation, which is remarkably induced again in the transient state. It is considered that these reconnection and rotation phenomena are induced by the Marangoni convection, due to the existence of the temperature gradient.

Recently, tunable color filters have been desirable for various applications such as tunable colored glasses, camouflage materials, smart labels, smart windows, and dynamic displays. Herein, we present an optical rotation-based color tuning (ORCT) method, which is a cost-effective and non-destructive way to provide a wide range of color tunability using a controlled cholesteric liquid crystal (CLC) as a chiral photonic crystal and two polarizers. Moreover, the color range of the ORCT can be manipulated by engineered optical rotation of the CLC film, which is verified by numerical calculations and experiments. As a proof of concept, tunable colored glasses are demonstrated to filter out unexpected light sources and provide better visibility. Our ORCT technology can be a cornerstone in potential color variation applications.

Cholesteric liquid crystals (CLCs) have a self-assembled helicoidal structure that results in vibrant reflective colors. These chiral nematic materials can be stabilized by in-situ photopolymerization of reactive liquid crystal monomers present in the CLC mixture to form so-called polymer stabilized cholesteric liquid crystals (PS-CLC’s). These PSCLCs exhibit several novel electric field driven optical responses, including color changing and spectral bandwidth changes. This changes are associated with electrical deformations of the polymer network and the surrounding liquid crystals response to the network deformations. Here we present our recent results in this area, including work to elucidate the mechanistic details of the electrically driven response and our application of this mechanism to other liquid crystals.

While hydrogen bonds are often used for the construction of supramolecular structures, the hygroscopic nature often decreases the adhesive strength. We have previously developed a light-melt adhesive with strong non-hydrogen-bonding cohesive force due to a two-fold π-stacking structure of V-shaped flapping molecules (FLAP). Here we have developed a new FLAP molecule, dppz-FLAP, bearing an electron-deficient dipyridophenazine (dppz) wings that enhances the cohesive force of the supramolecular materials by constructing tighter two-fold columnar π-stacking structure. This material shows viscoelasticity and liquid-crystalline properties by introducing peripheral long alkyl chains. Actually, dppz-FLAP demonstrates high shear strength over 1 MPa as a supramolecular adhesive. Since the dppz-FLAP adhesive only needs to be pressed at room temperature for the adhesion process, it could be categorized into a pressure sensitive adhesive (PSA). Interestingly, the dppz-FLAP film pasted on a PET tape showed virtually no peeling stress. Therefore, dppz-FLAP is the first liquid-crystalline pressure sensitive adhesive (PSA) that shows high shear strength with easy peelability.

This presentation demonstrates the use of drop-on-demand printing for the fabrication of liquid crystal (LC) droplet devices tailored for a range of different applications. The presentation will begin with a demonstration of the printing of different LC inks in the form of nematic LCs and polymer-stabilized chiral nematic LCs. Results are presented to demonstrate how the latter can be printed as arrays to form switchable smart windows with embedded images. We then show how printed nematic LCs can be used to generate optical vortex beams under certain applied voltages and how they can be used to enable single-shot Stokes polarimetry.

Optical properties of selected photonic microstructures based on BP LCs doped with gold nanoparticles (Au NPs) are discussed. It has been shown that the examined photonic microstructures can provide promising tunable optical properties, simultaneously enhancing temperature stability of liquid crystalline microstructures. This is due to the presence of Au NPs with an appropriate organic coating in the LC matrix. It has been demonstrated that the investigated BP LC-based photonic microstructures seem to be very promising materials for realizing electro-optical modulation and switching as well tunable filter applications and sensing capabilities providing better transmission properties for perspective emerging tunable photonic devices.

Flat optics based on liquid crystal (LC), such as diffractive waveplates and LC spatial light modulators, have various applications in astronomy, optical communications, augmented/virtual reality, and LiDAR sensing. These applications demanded that LC flat optics actively controls the modulated wavefront. This study fabricated an LC grating device with periodical pretilt angle distribution by a novel photoalignment method. The photoalignment method uses an ultra-violet-light-treated polyimide alignment film. It was demonstrated that the LC grating could actively control the light propagation direction by the applied voltage. The proposed device comprises a photoalignment layer with gradually changed surface-free energy and flat electrodes on the entire surface without pixels and patterns. The photoalignment can use grey-tone masks, where the transmitted light-intensity profile is distributed. This study provides a suitable method for device fabrication, like in a flat panel display, and the proposed device finds potential applications.

An optically addressable liquid crystal spatial light modulator (SLM) is used for dynamic laser beam shaping used in a unique, fast metal additive manufacturing process (3D printing) [1]. We address challenges of using our SLM exposed continuously to high power kW-MW lasers. Control of liquid crystals is coupled to the optical-response of the photoconducting insulators that affects contrast, switching speed, and laser power handling. We compare liquid crystal materials laser damage rationalized based on their thermal properties, and highlight device-level stresses via computational modeling. Key areas of liquid crystals and semiconductor properties are presented that impact optically addressed SLM for power switching applications. [1] https://www.seurat.com/area-printing

Unlike any other technology, planar optical components based on geometrical phase modulation can combine fundamentally 100% efficiency in broad spectral bandwidths and for wide range of angles. Their truly planar and smooth structure ensures no haze and provides an opportunity for anti-reflection coatings further enhancing transmission. As, essentially, diffractive waveplates, they allow integration of multiple layers for complex spectral and polarization engineering. Achieving perfection is not easy though since it requires meeting tight tolerances on a multitude of fabrication processes and materials. We will present the results of tolerance analysis for different architectures of geo-phase optics, and will discuss the performance of some of most challenging components we have been fabricating.

We present a versatile characterisation of liquid crystal devices, including those integrated with organic photovoltaics. Photovoltaic thin film serves as an alignment layer and also generates an electric field under illumination that reorients liquid crystals for self-activated or autonomous operation. Apart polar alignment angle, anchoring energy, thickness uniformity, the photovoltaic properties, such as the photovoltage generated and photoconductivity, are captured and the map of the spatial changes of the parameters can be created. The method is applicable to other liquid crystal systems, such as doped liquid crystals and optically thin cells, with phase lag as small as π.

Lasers offer highly desirable characteristics for imaging and display applications, including high directionality, intensity, and potential for a wide color gamut. However, the coherence of laser light leads to the formation of speckle, a spatially distributed granular distortion caused by interference. In this presentation, we demonstrate novel liquid crystal (LC) active screens that enable a significant reduction in the speckle noise for RGB laser illumination sources. The advantages of the active screen approach are then highlighted in comparison to LC speckle reducers used in transmissive geometries. We conclude by considering the impact of the active screen configuration on image formation.

Spatial light modulators (SLMs) play a key role in modern optics and imaging applications, enabling dynamic control over the phase, amplitude, and polarization of light. For next-generation applications, there is a need for SLMs to exhibit 2 phase modulation within 1 ms at low applied voltages. In this presentation, we investigate the optical phase modulation potential of different nematic liquid crystal (LC) devices including the pi-cell operating in the so-called symmetric H state. Experimental results obtained using a phase-shifting Michelson interferometer confirm full 2 phase modulation in 1 ms, which is in good agreement with results from simulations.

Optical vortices are of particular interest due to their numerous applications resulting from their orbital angular momentum. In this work a system for forming optical vortex beams based on the properties of nematic liquid crystals will be presented. It allows for the creation of vortices with different polarizations and different vortex charge, controlled by an electric field. Additionally, results showing nonlinear self-focusing of the vortex leading to diffraction compensation will be presented. Both reorientation nonlinearity and self-focusing thermal nonlinearity were used to create a self-trapped optical vortex propagating at a distance of the order of mm.

In the glass or gel states, materials have perfect isotropic symmetry and transparency. However, even if physical quantities such as density, concentration, and orientation are uniform, spatial heterogeneity in mobility may appear, which is called “dynamic heterogeneity”. we have invented a new fluctuation microscope that directly visualizes the dynamic inhomogeneity. In this report, as a model system for observing dynamic inhomogeneity, we observed swollen liquid crystalline nematic gels and polymers. Orientational order is encapsulated in polymer chains. Both dynamics of the nematic director and conformation of polymer chains are dynamically coupled with each other. We have recorded this polymerization process using a fluctuation microscope from immediately after UV irradiation, and directly confirmed that the dynamics of the orientation fluctuation gradually decelerates with the passage of polymerization process. We also success to confirm that the dynamic inhomogeneity appears in space, based on the time evolution analysis of the image of special distribution of the amplitude and the relaxation time of the director fluctuation observed by the fluctuation microscopy.

This paper explores how Liquid Crystal (LC) technologies can enable the metaverse by enhancing Augmented Reality (AR)/Virtual Reality (VR) optics. We highlight the potential of Liquid-Crystal Polarization Holograms (LCPHs) developed by Reality Labs Research (RLR) at Meta Platforms, Inc. LCPHs offer compact, lightweight solutions with versatile optical capabilities, including eye-tracking, accommodation, compact VR viewing optics with improved image quality, AR waveguide combiners with enhanced efficiency, and simplified fabrication processes. These advancements show promising potential to make a real impact in the AR/VR industry. LC technologies, especially LCPHs, are paving the way for more comfortable and immersive AR/VR viewing experiences.

Since 1979, liquid crystal lenses have been a target of perfect parabolic lenses. However, the constraints of the so-called power law coming from the physics and chemistry of nematic LC limit the development in large-aperture GRIN LC lenses. In this study we present electrically tunable progressive lenses utilizing nematic liquid crystals (LC). The proposed LC lens is capable of dynamically adjusting its focal length, functioning as either a positive or negative lens. Our findings reveal that the spatial distribution of lens power within the progressive LC lens, ranging from +4D to -3D, far surpassing the range of -0.87D to +0.87D which one may expect within the parabolic wavefront approximation. For a lens with a 30 mm aperture a total tunable range is 7.6 D (from +5.6D to -2D) which is 4.75 times larger than the traditional parabolic prediction~1.6D (from +0.8D to -0.8D). This study not only challenges conventional limitations set by optical phase differences in gradient-index LC lenses but also paves the way for transformative advancements in optics and beyond.

Liquid crystal polarization holograms (LCPH) have demonstrated optical characteristics which are well suited for virtual and augmented reality (VR/AR) applications. To enable complex LCPH designs, an internal tool based on rigorous coupled wave analysis (RCWA) and the Berreman 4x4 method has been developed. This tool, named LCPro, allows for the design, simulation, and tolerancing of complex LCPHs. Several design case studies with differing applications in AR/VR will be discussed where inverse design techniques are used to solve for the required structure given a desired optical response.

Head mounted display systems are now widely available, yet there are still key technical challenges to increase their market appeal. One such challenge is the conflict for the human vision between accommodation and vergence when viewing virtual content. At worst this leads to an uncomfortable viewing experience and at best it places limits on the projected content. The transition from fixed focal length optics to systems that can be tuned to match the virtual content promises to change this paradigm. In this paper we describe tunable liquid crystal lens based on Frensel optics that allow variable focus of the virtual image. Crucially this is the first time this type of lens has been made with ultra-thin, light bioplastic films instead of glass uniquely enabling attractive product form factors. We will showcase the performance attributes of the lenses and describe the cost effective manufacturing approach we have pioneered for making these ultrathin lenses in conventional flat panel display factories.

It is known that in uniformly oriented liquid crystal cells subject to uniform external electric field, pairs of topological defects of unitary topological charge of opposite sign appear spontaneously as result of symmetry breaking. They attract each other and annihilate to release the elastic constraint associated with director distortion around defects. Several techniques have been reported to date in order to control the location of generation of individual topological defects and their isolation from surrounding defects to secure their stability and provide large working area around the defect core. Here we will present our recent progress in controlled generation of self-engineered topological defects in vertically aligned nematic cells using structured electric and magnetic fields. In particular, we will report on ways to control their characteristics (e.g., spatial extent, core size, topology) in the context of developing advanced tunable liquid crystal diffractive waveplates for beam shaping and high-contrast imaging applications.

We present a liquid crystal (LC) optical vortex (OV) beam generator that is tuneable in both wavelength and orbital angular momentum state. Two-photon polymerization direct laser writing is used to structure the director profile of a polymerizable LC in 3-dimensions to form a helicoidal phase plate. Here, we demonstrate an OV beam generator that can be electrically tuned to produce any integer or fractional OV from zero to second order, for incident wavelengths in the range 490 nm and 780 nm. A range of techniques are employed to characterize and verify the OV beam generation at different voltages.

Nanoparticles of various shapes and sizes can affect the optical properties and stabilization of blue phase liquid crystals (BPLCs) due to the various compatibility with the LC host. Nanoparticles (NPs) that are highly compatible with the LC host can be dispersed in BPLCs of both the double twist cylinder (DTC) and disclination defects. We present a systematic study of the phase behavior of BPLC using CdSe nanoparticles with three different shapes (spheres, tetrapods and nanoplatelets) with identical cores and nearly identical long-chain hydrocarbon ligand materials. The spherical NPs are more compatible with the LC host than the tetrapod shape and platelet shape NPs, showing a wider temperature range of BP and a redshift of the reflection band of BP. While the inclusion of spherical NPs significantly tunes the optical properties of BPLCs, BPLCs with nanoplatelets have limited impact on the optical properties and stability of BPs due to poor compatibility with LC hosts. We report that the optical behavior of BPLC can be tuned by the type and concentration of NPs.

The two-dimensional array of microlenses used in Shack Hartmann wavefront sensors (SHWS) is an important element. Fabrication of such microlenses, however, can be an expensive and tedious process as it involves several stages that require high precision. These stringent fabrication conditions place limitations on its uses for different applications that require ease in alteration of parameters such as the number of elements, diameter of the lenses, and focal length of the array. In the present work, we demonstrate the implementation of inkjet-printed liquid crystal (LC) microlens arrays as a reliable alternative to that of the conventional microlenses used in SHWS. The fabrication of bespoke LC microlenses is rapid and economical and offers a number of flexibilities to easily tailor key parameters based on user requirements. Proof-of-concept experimental results are included that demonstrate the applicability of the LC microlens arrays for wavefront sensing.

Speckle reduction is important in interferometry-based arrangements in order to improve the accuracy and precision of the measurement as such speckle patterns can obscure the underlying fringes, making it difficult to analyze or interpret the results. In the present work, we demonstrate the implementation of a chiral nematic liquid crystal (LC) based diffuser as a tool to mitigate the influence of speckles in an interferometry arrangement. Such LC based diffusers are controlled by adjusting the applied voltage to modulate the phase of the incident light dynamically to create a temporally varying random phase mask that can reduce the impact of spatially varying speckle noise. Proof-of-concept experimental results are included to demonstrate the reduction of speckle in an interferometric arrangement using chiral nematic LC materials. Quality metric parameters are also defined to analyse and quantify the amount of reduction for different values of the applied voltage to the LC diffuser.