This pdf file contains the front matter associated with SPIE Proceedings Volume 12658, including the Title Page, Copyright information, Table of Contents and Conference Committee lists.

Liquid crystal (LC) elastomers exhibit remarkable mechano-optical properties, combining the elasticity of elastomers with the molecular orientation of LCs. These unique characteristics have spurred the advancement of next-generation applications, including wearable optical sensors, reconfigurable photonic materials, and solar energy harvesting. Nonetheless, achieving dynamic control over both mechanical deformation and molecular reorientation remains a challenge due to the viscoelastic nature of LC elastomers. In this study, we propose a straightforward approach to tune the recovery response of mechanical deformation and molecular orientation just by simply introducing external layers in elastomer films. Through this material design, we can achieve the desired mechano-optical properties in multilayered LC elastomers. By strategically modifying the external layers, we can tailor the viscoelasticity and enhance the recovery response of the LC elastomers. Our proposed concept provides a versatile platform for the development of high-performance and multifunctional stimulus-responsive materials. By optimizing the recovery response of both mechanical deformation and molecular orientation, we can unlock new possibilities in the field of mechano-optics, enabling the creation of advanced devices with improved functionality and performance.

The chiral nematic phase of cellulose nanocrystals (CNC) in the suspension liquid state is commonly examined using polarized optical microscopy (POM) as it conveniently reveals the cholesteric pitch through fingerprint textures. However, POM has certain limitations, one of which is the requirement for a perpendicular alignment of the chiral axis with the optical axis to achieve accurate measurements. We propose employing SHG microscopy as an alternative technique, offering high-contrast imaging of the chiral nematic phase with inherent 2-photon confocal effect. An IR pulsed femtosecond laser is raster scanned through the microscope, and the cumulative SHG response of the aligned CNC recreates the fingerprint textures. As is shown in this present work, the tight focussing effect of SHG microscope allowed z-scanning to render high contrast 3D models of the structures. Morphological observations and the tracking of defects in 3-dimensional space was made possible.

An approximate beam propagation method is proposed as an intuitive simulation of the optics of Pancharatnam–Berry phase (PPD) and polarization volume hologram (PVH) devices. Using this method, the connection between, and polarization properties of, these two types of devices are made clear.

Nonlinear optical (NLO) materials whose optical properties change in accordance with incident light intensity are attracting much attention in various fields. Liquid crystals (LCs) exhibit the largest nonlinearity among functional materials due to their photoinduced molecular reorientation. In particular, doping dichroic oligothiophene dye into LCs increases the light sensitivity of materials based on the interaction between dyes and an optical-electric field. Furthermore, the absorbance of this LC system drastically increases through the dye molecules' reorientation, promising. for application to the optical limiter; however, practical applications require better light sensitivity. In this study, we investigated the effect of the host LC structure such as fluorinated LCs on optical limiting behavior derived from nonlinear molecular reorientation. Irradiation of dye-doped LCs with a laser beam brought about molecular reorientation, and the transmittance decreased with an incident light intensity. Furthermore, the threshold light intensity for optical limiting behavior depended on the host LCs structure. Trifluorinated LCs effectively increased the light sensitivity of the dye-doped LCs compared to LCs without fluorine substituents. This result contributes to the material design for the low threshold optical devices utilizing the NLO of dye-doped LCs.

Liquid crystals are transparent optically birefringent materials that have the ability to self-assemble into tunable photonic microstructures. They can be modified by adding chiral dopants, by anchoring on confining surfaces, temperature changes, and by external electric or magnetic fields. Cholesteric liquid crystals (CLCs), which have a periodic helical structure, act as photonic crystals and thus partially reflect light with wavelengths comparable to the period of the structure. Possessing these properties, CLCs can be utilized as resonators or even as micro-lasers if doped with organic dye. In this work, we present the findings of a numerical study of light transmission through CLCs with or without isotropic defect layers in different 1D geometries. We also show numerically calculated photonic eigenmodes and their corresponding Q-factors. Overall, this work summarizes the properties of CLC resonators that could be important for the design of liquid crystal micro-lasers and other soft-matter-based photonic devices.

A possible large quadrupole moment driving torque is discussed in terms of phenomenological observation of specific smectic liquid crystal cases. Some smectic liquid crystal molecules showing their molecular directors tilting from the smectic layer normal are forced to stay the directors perpendicular to the smectic layer normal by strong azimuthal anchoring at the surface of the liquid crystal panel. This specific configuration is called as SSD or Smectic Single Domain drive mode. An SSD liquid crystal drive mode has been found of its molecular director switching keeps perpendicular to the applied electric field during its whole the switching process. Although it is still not a direct proof, this empirical observation is one of the possible pieces of evidence of quadrupole moment driving torque. So far, all the empirical observations indicate quadrupole moment driving torque in an SSD liquid crystal panel.

Lenses with tunable focal lengths play important roles in nature as well as modern technologies. In recent years, the demand for electrically tunable lenses and lens arrays has grown, driven by the increasing interest in augmented and virtual reality, as well as sensing applications. In this paper, we present a novel type of electrically tunable microlens utilizing polymer-stabilized chiral ferroelectric nematic liquid crystal. The lens offers a fast response time (5ms) and the focal length can be tuned by applying an in-plane electric field. The electrically induced change in the lens shape, facilitated by the remarkable sensitivity of the chiral ferroelectric nematic to electric fields, enables the tunable focal length capability. The achieved performance of this lens represents a significant advancement compared to electrowetting-based liquid lenses and opens exciting prospects in various fields, including biomimetic optics, security printing, solar energy concentration, and AR/VR devices.

We report a room-temperature dual-frequency field assembly technique that is capable of fabricating large-areal size (~cm2 or larger), well-aligned cholesteric liquid crystals to thicknesses up to 2.2 mm, corresponding to period number N (thickness/index grating period) of nearly10,000 in the visible spectral regime. The method employs successive application of low- and high- frequency electric field on a thick cell of CLC starting mixture containing a nematic constituent of negative anisotropy. The low-frequency field creates conductive hydrodynamical instabilities that mash the mixture to a state with completely randomized orientation of the cholesteric helices; the next application of a high-frequency field at a field strength below the dielectric hydrodynamic instability reorient all the helices into uniform standing helices. Such extraordinarily thick chiral photonic crystals exhibit many never-before-realized chiral photonic properties such as giant rotation of optical polarization with high transmission (low scattering loss), polarization switching and ultrafast pulse modulation capabilities for visible to mid-infrared lasers, in addition to dynamic tunability by electrical, thermal, or optical means.

We explore the structures and confinement-induced edge dislocations in Grandjean-Cano wedge cells filled with the recently discovered chiral ferroelectric nematic (NF ∗ ) and chiral antiferroelectric smectic-Z (SmZA ∗ ). The chiral mixture is formed by DIO mesogen doped with a chiral additive. Wedge cells with parallel and antiparallel rubbing at the opposite plates show quantitatively different structures which is attributed to the polar in-plane anchoring of the spontaneous polarization at the rubbed substrates. The helical pitch shows a non-monotonous temperature dependence upon cooling, increasing as the temperature is lowered to the N ∗ -SmZA ∗ phase transition. The SmZA ∗ formed from an untwisted N ∗ in the thin portion of the wedge shows a bookshelf (BK) geometry, whereas the twisted N ∗ transforms into a twisted planar (PA) SmZA ∗ structure. In the NF ∗ phase, the untwisted N ∗ becomes twisted in a wedge with antiparallel assembly of plates and monodomain in wedges with parallel assembly. The twisted regions of NF ∗ show only one type of Grandjean zones separated by thick edge dislocations with Burgers vector 𝑏 = 𝑃; the neighboring regions differ by 2π- twist.

Nowadays, augmented reality (AR) systems and virtual reality (VR) systems still suffer from two main problems related to human eyes. One is vergence accommodation conflict (VAC) and the other is vision corrections. To resolve those problems, we could use dynamic lenses to provide extra lens powers for changing the image plane of AR or VR systems and correcting vision. In this research, we used polarization-switching-type liquid crystal lenses as a varifocal lens and combined three liquid crystal lenses as a liquid crystal lens set. With applying different voltage, liquid crystal lens set exhibits four operating modes. Four operating modes present three electrically tunable lens powers: 0, -0.79 diopters, -2 diopters, and -3.06 diopters by means of passively anisotropic polymeric layers as well as active manipulation of polarization of incident light (<50 ms). Furthermore, we demonstrated the practical application of the LC lens set in AR and VR systems, effectively presenting its ability to perform varifocal image. This solves both the problems of VAC and vision correction in AR and VR systems. By adjusting the LC lens set, it could display even 7 switching modes and the lens power ranges from 0 to -4.5 D.

Emulsions typically form with spherical boundaries due to the isotropic nature of surface tension. When a liquid crystal phase separates into two distinct phases highly non-spherical boundaries can be produced due to the elastic forces of liquid crystal and anisotropic surface tension which is director dependent. SEM imaging allows us to visualize the two distinct phases of liquid crystal and observe interesting responses to vacuum and electron beam excitation. Heating the sample also reveals the existence of two bubble phase transitions associated with the two liquid crystal phases. Utilizing the potential of liquid crystal phase separation can lead to new materials such as hexagonal blue phase, stable cholesteric tactoids and improve the design of other blue phase mixtures.

This review provides an overview of the wide-ranging dynamical nonlinear- and electro- optical responses of liquid crystals and reexamine some exemplary photonic applications such as smart windows/display, tunable/reconfigurable metamaterials or metasurfaces, plasmonic nanostructures, micro-ring resonator, and chiral photonic crystals for polarizations and manipulations of ultrafast pulsed lasers of complex polarization states.

Flexible liquid crystal displays require the same performance as standard displays, ideally, even when they are bended, which poses requirements also to materials used for the various working functions. Sheets formed by aligned carbon nanotubes are flexible, electrically conductive and quite transparent thus attractive as electrodes but also as aligning layers for LC flexible displays. Unidirectional planar alignment of nematics can be obtained with CNT sheets, even if there are still many open issues. Here we study optically and dielectrically the magnetic field reorientation of nematic LC aligned by CNT sheets, more specifically, of 5CB in CNTs - TN cells.

Metamaterials have subwavelength periodic structures that manipulate electromagnetic waves. Typically, difficulties are encountered in fabricating this type of materials due to the sophisticated techniques involved in their creation. Bubble domains in chiral nematic liquid crystals present a skyrmion lattice which has periodicity regions along a cell, which allow the observation of unconventional light-matter interaction. However, the interaction dynamics between vortices presents a challenge to ensure the order of the lattice throughout the space it covers. In this work we study the use of liquid crystal microdroplets as potential wells and the clustering of topological defects in them.

By the application of electromagnetic fields onto an homeotropic nematic liquid crystal cell it is possible to induce vortices, which are particle-type defects with topological charge. The dynamics of the vortices is such that topological charge of the system is conserved, so these defects are always induced in pairs that annihilate after a short amount of time. Using a magnetic ring it is possible to induce a stable vortex triplet that allows the study of its dynamics, which is of an oscillatory kind when a low-frequency voltage is applied. Experimentally, we determine the region of parameters where the vortex triplet is stable, unstable, or becomes a lattice of vortices. We propose an amplitude equation which allow us to describe the vortex dynamics, and numerical simulations show agreement with experimental observations.

The development of multifocal microlens array has paid many attentions recently with the applications of plenoptic cameras, stereoscopic displays, and beam homogenizers. A variety of technologies have been explored and applied to produce multifocal microlens arrays, however, most multifocal microlens arrays are limited due to structural modification, long fabrication time, and lack of tunability. In this study, we present a novel method of fabricating a tunable multifocal liquid crystal microlens array (TMLCMA) using the three-electrode structure composed of a large hole, small-hole array, and planar electrodes. Liquid crystals with positive dielectric anisotropy were filled in the TMLCMA sample and aligned planar with antiparallel rubbing treatment. A modal layer was deposited on the surface of the large hole electrode to assist in extending the fringing electric field into the TMLCMA center. The fringing electric field induced by the large hole electrode results in the microlenses have different focal lengths from the TMLCMA border to the center. The TMLCMA can be worked in concave and convex modes on the basis of signal control schemes. The beam patterns through the TMLCMA are observed and the phase shifts of the microlenses at various positions are reported. The optical imaging of the TMLCMA has been demonstrated practically. The results reveal that the proposed method is able to produce a tunable multifocal microlens array via a simple fabrication and addressing scheme. This study has proposed a strong basis for the further development of microlens array, and the optical characteristics of the TMLCMA are promising to applications of optical fields.

We demonstrated an image-based polarization detection system comprising 4 tunable liquid crystal wave plate and 4 polarizers for the measurement of full Stokes parameters and material recognition with a single shot. In this paper, based on polarization property, the metal plate and the glass substrate could be recognized. The one of the applications is to provide a practical way in image-based polarization detection in Advanced Driver Assistance Systems for material recognition which could help in driving safety.

Coaxial- and counter-optical setups for laser ultrasonics using a photorefractive liquid crystal were fabricated. The laser ultrasonics involves irradiating an object with a laser pulse to produce an ultrasonic vibration, and then using another laser beam to detect the vibration. The phase of the laser beam reflected from the object is shifted by the ultrasonic vibration. By using liquid crystals with photorefractive properties, the resulting phase shift of the laser beam reflected from the material can be detected. Compared to traditional laser ultrasonic methods, this system offers a simpler optical setup and allows for more precise measurements that are unaffected by environmental vibrations.