This PDF file contains the front matter associated with SPIE Proceedings Volume 12907, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

Cholesteric Spherical Reflectors (CSRs) are omnidirectional selective retroreflectors enabled by the ability of cholesteric liquid crystals (CLCs) to self-assemble with helicoidally modulated long-range orientational order, turning them into a liquid chiral photonic crystal with one-dimensional periodicity. The liquid state allows us to easily mold the CLC into spherical units, with stabilizers in the surrounding liquid phases ensuring the appropriate boundary conditions. By varying the composition of the CLC we can continuously tune the wavelength band of retroreflection across the visible spectrum and into the ultraviolet (UV) as well as infrared (IR) regimes, choose whether the CRSs reflect right- or left-handed circular polarization, and we can make them polymerizable, such that the CSRs are easily turned into solids after annealing, allowing easy manipulation and incorporation into diverse matrices. This opens for numerous innovative applications, from anti-counterfeiting and supply chain track-and-trace solutions, via human-invisible signage optimized for robots and AR device wayfinding, to the pixelation of structural color for generating non-spectral colors without absorption or indiscriminate scattering, and even enhanced-sensitivity disease testing. In my talk, I will briefly introduce the concept of CSRs and highlight their salient features, and then I will focus on our on-going efforts to solve important societally and industrially relevant problems by taking advantage of the opportunities offered by CSRs.

Viologens that exhibit a low-order liquid-crystalline (LC) phase at ambient temperatures can be used photo-sensitive moieties in LC materials. We synthesized viologens having an asymmetric core, while maintaining its stimulusresponsive properties, with the aim of forming a low order LC phase at ambient temperature. The obtained viologens having an asymmetric core exhibited low-order LC phases with no regularity in the direction of the molecular short axis. Furthermore, we synthesized a viologen derivative having a symmetric core. We found that the development of loworder LC phases was observed, when the rod core was asymmetried by changing the position and number of ionic bonds. It was suggested that the intermolecular interactions were weakened by varying the position of the ionic bonding sites to asymmetrize the core. The photo-responsive behavior of the viologen having an asymmetric core was investigated. The viologen having an asymmetric core was mixed with the nematic LC compound (5CB and 7OCB) to prepare homogeneously aligned films. The change in the alignment of the mesogens was successfully induced by triggering a one-electron reduction reaction of the viologen moieties by light irradiation.

In the past decade, liquid-crystal network (LCN) technology has been used for the development of soft actuators based on the controlled reversible changes of the order parameter of the oriented polymer network. Various deformations ranging from simply bending or curling to complex origami types of morphing are demonstrated. Herein, the work on using LCNs for soft robotic applications in pick-and-place operation. This was achieved through our suction-cup-based gripper that mimics the reversible self-generated vacuum within cephalopod-limb suckers. Our gripper can generate attachment forces up to 4000 times the weight of the gripper, comparable to the sucker of a live octopus.

Numerous rod-like organic molecules self-organize into layered structures, as demonstrated in various systems, including smectic liquid crystals, micelles, and lipid bilayers, owing to side-by-side intermolecular interactions. These layered structures are of interest to another class of layered molecular assemblies in the solid state, namely, small-molecule organic semiconductors (OSCs). Many OSCs are composed of various π-electron cores substituted with flexible side chains. Layered-structure formation is important in OSC systems because it enables the production of aligned molecular layers interfaced with gate dielectric layers, which are used to fabricate high-performance organic thin-film transistors (OTFTs). Using these rod-shaped OSCs, we developed a technique for fabricating single-crystal thin films of uniform thickness at the molecular level by introducing a geometric frustration effect between the layers. We also selectively produced crystalline polymorphs with distinct herringbone packing motifs. By producing these layer-controlled films on the trap-minimized surface of gate insulators, we fabricated OTFTs exhibiting sharp on/off switching characteristics approaching the Boltzmann limit. In this paper, we introduce recent techniques for the rational design of organic semiconductors.

Cascaded spiral diffractive lenses (cSDL) based on liquid crystal (LC) technology, offer low voltage (⪅10Vrms) direct addressing, for wide aperture (>25mm OD) transparent lenses with very high fill factors (>98%), and broad tunable focal range (>4 Diopters). The two cascaded devices are conventional LC cells, manufactured using a single direct laser writing lithographical process on a transparent ITO covered glass substrate. In this presentation we will present our latest results, employing dual frequency materials, the use of the lenses in zoom systems, and in dynamic achromatic image capture. We will present implementations with both 24 and 72 electrodes, allowing for quasi analogue tuning in the whole tuning range. We will also present the employed direct addressing electronics.

It is difficult to immobilize a single capsule with liquid crystalline shell (LC capsule) for observation. Referring to the microwells generally used for observation of living cells, we fabricated tailor-made microwell using a three-dimensional (3D) printer to match the size of the fabricated LC capsules. We found it works well as the container for LC capsules. We demonstrate the observation of the lasing of the immobilized LC capsule.

Offering an ultrathin formfactor and lightweight, diffractive liquid-crystal optics is a promising tool to design a more compact VR display system. However, the severe chromatic aberrations of this diffractive elements need to be solved before further practical applications. Here, we come up with an achromatic system consists of three diffractive liquidcrystal components to address this longstanding color issue. The phase and spectral response of each element are specifically designed to manipulate the polarization states of light and compensate the chromatic aberrations. A significant improvement in color performances has been demonstrated with both our simulations and experiments. Potential applications for metaverse, spatial computing, and digital twins that have found widespread applications in smart tourism, smart education, smart healthcare, smart manufacturing, and smart construction are foreseeable.

A new approach to a tunable Pancharatnam phase beam steering device is proposed that can steer NIR light to angles greater than 10 degrees with greater than 80% efficiency.

Terahertz (THz) waves have attracted significant attention for many years mainly because of their practical applications in imaging. Liquid crystals (LCs) are remarkable materials for THz wave polarization modulation, as external fields with low power consumption can control their birefringence. Previously, we demonstrated a continuous wave THz common path phase shifting interference (PSI) method using the hydrogen-bonded LC phase shifter. In this study, we introduce the magnetic field to enhance the operation speed of the hydrogen-bonded LC phase shifter. We discuss the magnetic field application methods and the operation speed of continuous wave THz common path PSI.

Photonic crystals manipulate light in unique and beneficial ways, acting as waveguides, laser cavities, and facilitating topological light propagation. However, the reconfiguration of photonic crystals has been limited, hindering their versatility. We have recently introduced the concept of pixelated 2D photonic crystals, where a pixelated matrix of the material enables variability in the dielectric profile. By changing the orientation state of liquid crystal molecules within individual pixels an effective refractive index for a specific input polarisation is altered. In this work we numerically show how different distributions of ”on” and ”off” state pixels and therefore different effective refractive index configurations in the periodically repeated unit cell effect the band structure of the material and its optical properties. Considering the size of pixels and unit cells, such photonic crystals would enable dynamic control of THz waves.

This manuscript presented the programmable metasurface based on LC (liquid crystal) material to manipulate the THz (terahertz) wave. To manipulate the EM (electromagnetic wave), the programmable and digital coding metasurfaces have been widely used in the microwave range using the semiconductor controlling elements (PIN diode and varactor diode). However, in the THz range, these semiconductor components have limited applications. Herein, a 1-bit digital programmable metasurface based on LC is proposed to achieve the THz wave manipulation with electrical control. The 1- bit digital coding metasurface is composed of two kinds of meta-atoms including “0” and “1” digital codes corresponding to the opposite reflection phase response “0” and “π” respectively. The reflection phase of the metasurface element is nearly 180° manipulating between biased (1) and unbiased (0) states of the coding sequence. When the different coding sequence is applied to the metasurface array, the phase profile between metasurface elements is changed dynamically and manipulate the incident THz beam. The proposed LC-based THz metasurface unit cell is applied with the different biasing voltages and in result the relative permittivity of the LC material is changed from 2.63 to 3.67 based on the orientation of the LC molecules. However, the resonant frequency is switching from 0.121 THz to 0.108 THz and achieved the 180 degree phase differences. Furthermore, 36x36 metasurface array is enabled to perform multi-functionalities including dual beam and multi-beam steering, beam splitting that could be implemented in the application of sensing, imaging, defence RCS (radar cross section) reduction and wireless communication such as RIS (Reconfigurable Intelligent Surfaces).

TE-mode optical switching by a liquid crystal device attracts interests both its application and scientific principle. Optical axis switching of the liquid crystal molecules perpendicular to the incident light provides TE-mode switching, which enables phase only switching without changing light throughput amplitude. A vertically applied electric filed to a planar aligned liquid crystal layer gives freedom to a liquid crystal panel configuration design. Such a TE-mode optical switching requires orthogonal driving torque of a liquid crystal molecules by vertically applied electric field. A typical dielectric driving torque does not provide such an orthogonal driving. A conceivable orthogonal driving torque is provided by quadrupole momentum. Liquid crystal layer’s parallel direction of polarization to the substrates may respond to the vertically applied electric field when the liquid crystal layer shows some quadrupole moment. This investigation tries influence of polarization direction of the liquid crystal layer originated from surface pre-tilt angle as well as its influence on electro-optical behavior.

We have developed angular-insensitive birefringent filters using discotic and calamitic liquid crystals. The filters show no angle dependence in oblique directions and the field of view exceeds +/- 60 degrees. Since the multilayer discotic and calamitic liquid crystal films have the same retardation in the oblique and normal directions, the filter achieves completely angle-insensitive optical properties. This optical filter is expected to be used in high precision and thin small devices in telecommunications and sensor applications.

We present a new liquid crystal-based device for correction of spherical aberration, which is commonly observed in microscopy and related methods. The device is significantly larger than previous direct laser written aberration correctors, measuring 1 mm across. The device operates in transmission mode for easy integration into the optical path and is capable of continuous greyscale tuning of up to a total amplitude of 2π rad. This device could present a cost effective and simpler to use alternative to traditional wavefront modulation technologies used in adaptive optics.