The helical nanofilament (HNF) structure formed by bent-core liquid crystals works as a good chiral motif to obtain induced optical activity. The superstructure of winding smectic layers in HNF exhibits excellent chiroptic functions, such as huge circular dichroism (CD) and optical rotation (OR) signals, through its non-trivial circularly polarized light scattering from the heliconical surfaces at the mesoscopic scale. Because of this principle, the optical activity observed in HNF is not considered as an intrinsic property of the molecules, but rather, extrinsic (induced) optical activity due to the helical structure. But this in turn means, this state can provide a useful environment to induce unique chiral responses in optical processes, not only ORD (transmission) or CD (absorption), but also emission (CPL: circularly polarized luminescence). Up to now, our group has demonstrated such induced optical activities based on bottom-up templating using HNF, to utilize its helical nanoporous structure that serves as a chiral environment (chiral nano-space) bringing about the chiroptic functions [2-3]. HNFs of a bent-core molecule were utilized as a three-dimensional mold, and thus the fabricated chiral nanoporous film has an inverse nano-helix structure. Upon refilling this inverse helix with an “achiral” nematic liquid crystal, distinct CD signals appeared due to the transfer of chirality from the inverse helix to the achiral nematic liquid crystal. The formation of the chiral superstructure was confirmed by the induction of CD signals. In addition, the induced CD signals can be readily modulated by external stimuli, such as the application of heat or an electric field. Amazingly, by refilling the chiral nanoporous film with a fluorescent nematic liquid crystal, it exhibits stimuli-responsive circularly polarized luminescence (CPL). In the present work, we will demonstrate an induced optical activity in nonlinear optical (NLO) process in a binary system of HNF and recently-found ferroelectric nematic liquid crystal. The second harmonic (SH) signals show a clear asymmetric behavior when stimulated by left- or right-circularly polarized fundamental lights. The proposed approach has vast potential for applications, such as for chiroptic modulators and switches, entangled photon generator, and biological sensors.

Organic photoactive materials with self-assembling behaviour have garnered significant attention due to their exciting potential to drive, tune, and control the optical properties of soft systems in a contactless manner [1, 2]. The incorporation of chirality and photosensitivity into self-organizing materials greatly enhances their functional capabilities [1, 3, 4]. These properties can be integrated into the molecular structure of liquid crystalline materials by incorporating appropriate chiral groups and photosensitive moieties [3, 5, 6]. Photoactive liquid crystalline materials formed by rod-like molecules represent a distinct class of materials that exhibit unique optical and electrical properties when exposed to light. Combining the anisotropic behaviour of liquid crystals with the ability to undergo reversible phase transitions or changes under light exposure, these materials are ideal candidates for a wide range of applications in sensors, imaging devices, and advanced optical systems [6-7]. In addition to various photosensitive groups such as spiropyran, stilbene, hydrazone, coumarin, diarylethene, and cinnamoyl, the azobenzene moiety is widely used for the design of both low-molar-mass and macromolecular liquid crystalline materials to make them photoactive [8-9]. The molecular structure specificities of calamitic photo-sensitive chiral materials play a crucial role on the formation of mesophases and the resulting structural and photo-optical behaviour. To deepen the understanding of the relationship between molecular structure, mesomorphism, and photosensitive properties, several recently designed photo-active materials will be presented. Lateral substitution on the molecular core of the calamitic liquid crystal proves to be an effective approach to tuning their mesomorphic and photoactive behaviour [10], with the chiral part of the molecule based on lactic acid [11-12]. The effects of lateral substitution with various halogen atoms and other groups in the vicinity of the azobenzene moiety on mesomorphic and photosensitive behaviour will be explored. Acknowledgments: Authors greatly acknowledge the financial support from the Czech Science Foundation [project CSF 23-42944S]. This work is also supported by the Bilateral Collaborative Czech-Taiwanese Project funded by the Czech Academy of Sciences [Project NSTC-24-12] and the National Science and Technology Council [Project NSTC 113-2927-1-027-502].

Counterfeiting represents a major global challenge, affecting various sectors, including documentation, pharmaceuticals, electronics, and consumer goods. Developing robust and multifunctional anti-counterfeiting technologies is imperative as counterfeit products become increasingly sophisticated. Cellulose nanocrystals (CNCs), derived from renewable sources, can form lyotropic liquid crystalline phases, offering unique photonic properties suitable for advanced security features. Their chiral nematic ordering enables selective reflection of left-handed circularly polarized light, while their structural colouration provides visible, non-reproducible patterns. Furthermore, CNC-based systems exhibit responsiveness to external stimuli such as humidity, temperature, and solvents, enhancing their functionality. In this work, CNC aqueous suspensions were converted via evaporation-induced self-assembly (EISA) into films that exhibit chiral polarised luminescence. To obtain this, fluorescent moieties were covalently grafted onto the CNCs, enabling the emission of circularly polarised light guided by the intrinsic chiral nematic architecture of the liquid crystalline suspension. The resulting materials integrate overt and covert optical signals, offering a promising platform for secure, sustainable, and scalable anti-counterfeiting technologies, as well as potential applications in photonic and optoelectronic devices.

In this presentation we will show how the introduction of a topological charge makes it possible to break the centrosymmetry of a conventional diffractive Fresnel lens, and thus enabling the addressing of the lens from the periphery, employing a single lithography step. The topological charge of the resulting spiral diffractive lens (SDL), introduces an orbital angular momentum to the passing beam, which may be eliminated by cascading two SDLs [1] or cascading an SDL with a spiral phase plate [2] with opposite charges. We will present our high power (+/- 50 dptr), 1 mm diameter implementations, as well as larger area lenses. The smaller lenses are adressed with only 4 electrodes, making them potentially compatible with wafer-level micro-optics. The compact lenses are characterised by a limited number of focal distances as well as a limited number of driving electrodes, while the larger 1” lenses present almost a continuum of focal distances.

Optical vortices are a special case of structured beams with unique properties and numerous applications. Due to the fact that they have orbital angular momentum and field uncertainty at the center of the beam, they are used in microscopy (including STED), optical tweezers, metrology, imaging, controlling the motion and quantum state, classical and quantum optical communication, etc. Optical vortices, like other optical beams, undergo diffraction broadening in homogeneous media. The generation of a diffraction-free vortex soliton is possible only in a few nonlinear media. Such medium are nematic liquid crystals, in which vortex solitons (vortex nematicons) have been obtained using both reorientational and thermal nonlinearity. Both nonlinearities have unique properties, especially they are nonlocal and very strong, which allow to observe vortex nematicons in milliwatt optical power. In this work the latest experimental results on the generation of vortex nematicons will be presented. In particular, it will be shown that the reorientation of the liquid crystal produced by the nematicon enables the transfer of orbital angular momentum between light beams. References: [1] H. Rubinsztein-Dunlop, et al., J. Opt. 19, 013001 (2017). [2] Y. V. Izdebskaya, et al., Optics Letters 40, 4182 (2015). [3] M. Kwaśny, et al., Optics Letters 45, 2451 (2020). [4] U. Laudyn, et al., Optics Express 28, 8282 (2020).

Liquid crystalline (LC) droplets represent a fascinating intersection of fluid dynamics, materials science, and optical physics, offering a unique platform for investigating complex phenomena such as topological defects, phase transitions, and responsive behavior under external stimuli. The study of LC droplets is further enriched by their sensitivity to external fields, such as temperature gradients and lightm [1,2] which can induce active motion and changes in their internal structure, demonstrating their potential as micro-robots or sensors in a broad range of technological and biomedical fields. Our previous research finds that light irradiation induces the collection of solute molecules within the LC droplet, leading to nucleation and aggregation of particles at the center, where topological defects are located. [3] Recently, the study has uncovered that the assembly of nucleated particles, even in the presence of only surfactant molecules, contradicts the initial assumption that light absorption by solutes is necessary for their incorporation into the droplet. Further investigation reveals the low light absorption of 5CB, a common LC material, in the near-UV region, which is instead observable through photoluminescence, indicating the importance of the excimer state of 5CB in the molecular uptake process. Experimental results demonstrate the formation of object assemblies in LC droplets under UV irradiation, with variations observed based on the type of solute and surfactant concentration. Figure shows (a) the photo-induced object after 8 min of 320 nm irradiation in an SDS solution, and (b) the photoluminescence reduction for different SDS concentrations. The study suggests that the excimer state of 5CB plays a crucial role in the photo-induced assembly process which was reduced when SDS was intake. The intake of solute molecules without specific molecular preference, and proposes that the aggregation of particles is induced by topological defects. The findings challenge previous assumptions about the conditions necessary for assembly formation and highlight the potential of using the excimer energy of 5CB for efficient solute molecule intake, providing new insights into the complex interactions within LC systems. [4]

Axially polar ferroelectric columnar liquid crystals (AP-FCLCs) have attracted attention for realizing ultra-high-density memory devices, provided that the polar direction of each column can be switched by an electric field (E-field) and retained after removal of the E-field. However, in most reported ferroelectric columnar phases, the induced polarity vanishes after the E-field is removed, making the realization of AP-FCLCs still challenging. We recently achieved ferroelectricity in the columnar LC phase of N,N’-bis(3,4,5-tri[(S)-citronellyloxy]phenyl)urea (Urea-(S)-cit), which contains six chiral alkoxy groups. In the columnar phase, the polarity of the compound was switched by an applied E-field and remained stable for over 7 hours after its removal, as confirmed by second harmonic generation (SHG). We clarified that the rigid helical columnar structure is essential for generating ferroelectricity, as it enhances intermolecular interactions within the column. However, one question remains regarding the origin of ferroelectricity: which chiral group plays a key role in generating ferroelectricity in the LC ureas? In this study, we regioselectively synthesized four diphenylurea compounds bearing (S)-citronellyloxy and decyloxy groups—N,N'-bis(3,5-di((S)-citronellyloxy)-4-decyloxy-phenyl)urea (1), N,N'-bis(4-((S)-citronellyloxy)-3,5-didecyloxyphenyl)urea (2), N,N'-bis(3-((S)-citronellyloxy)-4,5-didecyloxyphenyl)urea (3), and N,N'-bis(3,4-di((S)-citronellyloxy)-5-decyloxyphenyl)urea (4) —and investigated the positional effect of chiral alkoxy groups on ferroelectricity through SHG, circular dichroism, and XRD measurements. As a result, we identified the key chiral alkoxy groups responsible for ferroelectricity and proposed a mechanism for stabilizing the polar structure.

The motivation for conducting the present research is given by encountering a new optical communication technology IOWN (Innovative Optical and Wireless Network) proposed by NTT, Japan for the forthcoming the 5th generation optical communication, [1] where advanced LCoS will be utilized for multiple wavelength selection using LC device with rapid - response speed. Since, the asymmetric optically compensated IPS, FFS, ECB, VA, and FLC are featured by the rapid response in the switching -off process; this is the reason why we use these four LC devices. This report will be done by updating a previous publication.[2] References: [1] K Takeda et.al. Nature Photonics, Vol.7, pp.569-575\ (2013). [2]S. Kobayashi, MCLC, Special issue 17,768(17)pp.928-946(2024).

The prominent self-organizing materials that are in the actual focus of scientists and engineers developing molecular machines as well as macroscopic functional devices are thermotropic liquid crystals (LCs). Chirality can be induced in LCs by using chiral mesogenic molecules and, since they are sensitive to their environment, by adding a chiral dopant into an achiral LC host. Chiral liquid crystals (CLCs) are fascinating materials themselves. Nevertheless, their properties can be further improved by the introduction of photosensitive and/or luminescent moiety – structural features that open the way towards many future applications [1]. In this contribution, we focus on our recent results in the search for novel photoactive CLCs using lactic acid and 1,1´-binaphthalene-2,2´-diol (BINOL) as basic chiral building blocks. These chiral units are combined with various luminescent and photosensitive moieties with the aim to create chiral, photoswitchable, luminescent liquid crystals. Among a plethora of possible luminogens, polyaromatic pyrene systems show exceptional properties for both study and further practical applications, as they are robust and exhibit long singlet lifetimes upon excitation, making excimer emission easy to observe and utilize [2]. However, when combined with the most common photoswitch - azobenzene - the luminescence is lost due to both intramolecular and intermolecular quenching. Such a problem is only a piece of an iceberg of problems when trying to prepare a new multifunctional material [3]. In this context, different strategies for the design of multifunctional dopants, their synthesis as well as their fundamental properties will be discussed.

This study investigates the biosensing potential of lyotropic chromonic liquid crystals (LCLCs), offering an alternative to conventional liquid crystal (LC)-based biosensing technologies, which predominantly rely on thermotropic LCs as signal-transducing media. The nematic phase of disodium cromoglycate (DSCG) and sunset yellow (SSY) was applied in the detection of disease biomarkers such as the cancer biomarker CA125 and SARS-CoV-2 nucleocapsid (N) protein. The biosensing platform was designed so that the formation of CA125 or N protein immunocomplexes induced molecular reorganization of planarly aligned DSCG or homeotropically aligned SSY, giving rise to changes in optical and dielectric properties of the nematic LCLCs (Fig. 1A,B). Quantitative analysis was performed through optical texture observation, transmission spectrometry [1], dielectric spectrometry [2], and haze measurement [3]. Leveraging the hydrophilicity of LCLCs, immunocomplex formation was monitored in real-time by solubilizing analytes in LCLCs and tracking optical response over time to analyze binding kinetics (Fig. 1C). Molecular docking results indicate that LCLCs bind more strongly to biomolecules than thermotropic LCs do, which may explain their higher detection sensitivity in biosensing. These findings highlight the potential of LCLCs as immunosensing media for advancing next-generation LC-based biosensing technologies in precision medicine.

Recently roof-shaped nematogens 1 with an anthraquinone core were identified to approach an optimum biaxial aspect ratio.[1,2] While biaxial aggregates of hundreds of nematogens have been demonstrated by NMR relaxometry, the macroscopically aligned biaxial nematic could not been confirmed to date. This is a common challenge encountered already in two intense research periods, during which several claims about the discovery of the thermotropic biaxial nematic phase of a low molar mass material have been opposed.[3] The present contribution highlights the study of a number roof-shaped molecules such as 1 and 2 with a slightly distinct substitution pattern. Combined comprehensive X-ray scattering and Solid-State NMR investigations reveal that only one of these nematic materials (1) shows a pronounced local interdigitation of the lateral chain along the minor director. This is realised by the long lateral chains pointing towards the anthraquinone core. The self-assembly mechanism enhances the local biaxial order in the nematic phase and impacts on the XRS order parameters of biaxial nematogens 1 and 2. The local freezing of the rotation about the molecular long axis is a prerequisite to find the delicate thermotropic biaxial nematic phase. Fréedericksz transitions of the nematic phases are studied in the presence of electric and magnetic fields to probe phase biaxiality. ________________________________________ Acknowledgments: This study is supported by the German Science Foundation DFG via LE1571/10-1 References [1] M. Lehmann, S. Maisch et al. Soft Matter 2019, 15, 8496-8511. [2] M. Lehmann, N. Scheuring et al. ChemRxiv 2024. DOI: 10.26434/chemrxiv-2024-h9jd8 [3] M. Lehmann in Biaxial Nematic Liquid Crystals (eds. G.R. Luckhurst, T. Sluckin), Wiley Chichester 2015, 333-367.

We propose the integration of a haptic liquid crystal polymer network (LCN) coating into optical displays, creating a next-generation touchscreen with dynamic haptic feedback (1). This innovative approach bridges optics and haptics, enabling displays to provide real-time tactile sensations through programmable surface deformations. The LCN coating responds to external stimuli such as temperature, light, and electric fields (2), allowing for localized texture changes, friction modulation, and pressure-sensitive feedback. This seamless integration transforms smooth glass surfaces into interactive, touch-responsive interfaces, enhancing user experience in consumer electronics, augmented reality, and assistive technologies. The ability to create programmable tactile patterns makes it ideal for visually impaired users, immersive gaming, virtual training environments, and advanced medical interfaces. By merging haptics with optics, this technology redefines human-machine interaction, paving the way for smarter, more intuitive touch interfaces in the digital age.

The optical field induced first-order bistable Freedericksz transitions in a nematic liquid crystal (NLC) remains one of the most existing and beautiful fields in the optics of liquid crystals. It was first predicted by Tabiryan, Zel’dovich and Ong [1,2], but the criterion for the existence of a first-order optical field induced Freedericksz transition (OFT) is considered to be experimentally unattainable due to the limitation of the NLC optical birefringence. The enhancements of the first-order OFT by an external magnetic or electric field were subsequentially predicted and confirmed experimentally. From the discussions in the OLC 2011, Simoni, Ong and Tabiryan reported the experimental observation of a first order OFT in a NLC doped by a small quantity of a dye with negative dichroism in 2013 [3]. In this talk, we first report our review of many NLCs and understanding that the criterion for the existence of a first-order OFT can be achieved by certain existing advance NLCs with a very optical birefringence of more than 0.35. We further analyzed the OFT in a NLC with a dichroic dye and by an oblique incident orientation light beam. We realized the possibility to obtain first-order OFT with different incident angle and dye material. We also studied the OFT in a NLC with a dichroic dye to generate topological solitons in frustrated chiral NLC with a milliwatt-power divergent light [4]. We employed an azobenzene dye dopant that induces a positive optical nonlinearity in a NLC, where the director reorients toward the extraordinary light wave, thus increasing the refractive index. Irradiation of the frustrated chiral NLC with a milliwatt-power light beam triggers the formation of various orientational structures. Specifically, we experimentally observed the formation of orientational soliton structures in dye-doped, frustrated chiral NLC, including the development and relaxation of metastable solitonic structures. References: [1] B. Ya. Zel’dovich, N. V. Tabiryan and Yu. S. Chilingaryan, Sov. Phys. JETP 54, p. 32 (1981). [2] H. L. Ong, Phys. Rev. A 28 (4), p. 2393 (1983). [3] F. Simoni, D. E. Lucchetta, L. Lucchetti, H. L. Ong, S. V. Serak, and N. Tabiryan, Opt. Lett. 38, 878 (2013). [4] S. Shvetsov, D. Darmoroz, T. Orlova, M. Rafayelyan, and H. L. Ong (submitted, 2025).

Liquid crystals and structures of liquid crystals are capable of diverse control over the flow-of-light at the wavelength level, as well as below and above. In this talk, I will present recent results on the emergent photonic phenomena in liquid crystal structures and. I will present the concept of pixelated photonic crystals, use of neural networks for optical reconstruction and/or prediction of liquid crystal fields and design of lasing modes by liquid crystal based resonators. More generally, the talk is aimed to emphasise selected possible exciting research directions in photonic liquid crystal soft matter.

The effects of external force on polymers have been actively studied for a long time. Initially considered a primary factor leading to polymer degradation, it has recently been re-evaluated as crucial for imparting advanced functionalities to polymers. However, the effect of mechanical stimuli deliberately applied to the growing polymers is still unknown. Recently, we developed a novel photopolymerization process using spatiotemporal lighting, which causes molecular flow during the photopolymerization, termed scanning wave photopolymerization (SWaP) [1-5]. In this study, we report molecular alignment patterning and efficient polymerization behavior under photoinduced molecular flow fields [6-8]. Photopolymerization with scanning UV light exhibited higher-molecular-weight polymers, with a reduction of 90% of exposure dose compared to photopolymerization with static uniform light. Aligned polymer main chains stabilize the induced molecular alignment patterns. Our proposed approach holds promise for an innovative polymer synthesis process and unique optical applications.

Cellulose is the main substance found in plant cell walls, which supports the plant, keeping it stiff and strong. Gelatin is derived from collagen, which constructs the skin and bones of animals. Both biological molecules form long chain of crystal-amorphous periodic nano structure, showing structural birefringence. In water, the long chain of nanocrystals self-assemble into twisted fibers, showing the optics of chiral nematic liquid crystal. With polarized optical microscope, the 3D structure of the twisted fibers are analyzed, and the location of the crystal-amorphous periodic nano structure can be identified. Schlieren texture of nematic liquid crystal is observed in gelatin hydrogel. In case of cellulose chiral liquid crystal, planar texture with oily streaks, fingerprint texture embedded in double twisted fibrils, and focal conic domains are identified experimentally. The self-assembled twisted fibrils align and fix the nano crystals. The cellulose chiral liquid crystal shows brilliant stable visible color appearance in room temperature in daylight. Cellulose and gelatin have excellent biocompatibility, biodegradability and bioactivity. Utilizing the self-assembly and optical appearance, they are excellent for engineered tissues, drug delivery, colorimetric sensors, and sustainable eco-friendly optoelectronics.

Liquid crystal (LC) materials, especially with high birefringence and low viscosity, are widely investigated in the 0.1–3.0 terahertz (THz) range [1-3]. Many interesting applications are expected and predicted for radar, sonar, acoustics, astronomy, seismology, communications, and medical imaging. From the application point of view, the most important is obtaining the low tangent of losses, high coefficients of tunability of LC materials, and short reaction times (switch/on/off times). These properties can be changed and adjusted to dedicated applications. Dielectric ( from 0 to more than 30) and optical anisotropies (from 0 to about 0.6) can be obtained and easily regulated. Polarization coefficients for liquid crystals are typically up to a few hundred nC/cm2. Recently, liquid crystal materials with remarkably high polarization coefficients (more than two thousand nC/cm2) have been synthesized at the Military Univ. of Technology. Our preliminary investigations have shown that modifying the structure of LC molecules can reduce the tangent of losses to a value of about 10-2, with tunability of about 40% and relatively short on/off times of a few milliseconds. New LC double frequency materials were investigated with low loss tangent in tunable phase shifter and beam steering for the 0.1 – 3.0 THz range. The properties of these solutions have been described, and acceptable parameters (switch on/off times) from the application point of view have been received. Consequently, the use of dual-frequency LC, especially doped with nanoparticles, can constitute novel tunable structures for beam steering in tunable THz devices. Acknowledgments: This work was funded by the National Science Centre, Poland, UMO-2023/05/Y/ST11/00238 M-ERA.NET 3 project. References: [1] Y. Cheng, et al., Optics and Lasers in Engineering, 146, 106700, (2021). [2] X. Fu, et al., ACS, Appl. Mater. Interfaces, 14, 22287−22294, (2022). [3] U. Chodorow, et al., Mol. Cryst. and Liq. Cryst., 657, pp. 51 – 55, (2017).

Six difluoro benzoic acid isomers were added to a hydrogen bonded liquid crystal (HBLC). Clearing temperature depends on the fluorine position on the phenyl ring. The dielectric constant, refractive index anisotropy, and elastic constants of K11, K22, and K33 of HBLC mixtures were also investigated in the nematic phase at room temperature.

Coloration in nature serves diverse functions such as camouflage and communication, with polarization-dependent coloration being one particularly intriguing mechanism. This phenomenon, observed in biological systems like marine animals and ferns, has inspired the development of artificial materials that replicate such optical behaviors. Among these, dichroic dyes exhibit polarization-dependent absorption due to their anisotropic molecular structure. When incorporated into liquid crystal (LC) matrices, their alignment can be finely controlled by the LC orientation, enabling tunable polarization-dependent transmission colors [1]. Despite advances in dichroic dye-doped LC films, limitations remain—particularly in achieving a full color gamut due to the broad absorption bands of dyes and challenges in generating specific hues such as green [2]. To address this, we propose an efficient strategy utilizing the optical rotation properties of cholesteric liquid crystal (CLC) photonic crystals with photonic bandgaps (PBG) in the near-IR region. These CLCs allow wavelength-selective polarization modulation while maintaining high visible transmittance [3]. By combining bilayer dichroic films with CLC substrates, we demonstrate that the optical rotation imparted by the CLC enables simultaneous wavelength- and polarization-selective absorption aligned with the films’ anisotropy direction, significantly extending the effective color gamut. Systematic analysis reveals that the interplay between the PBG position and alignment direction critically influences the resulting transmission colors. This approach provides a simple yet powerful method for enhancing organic dye-based coloration, with promising applications in smart windows, color filters, and display technologies.

Geometric phase liquid crystal (LC) optical elements possess a spatially varying optic axis distribution and thus diffract light. Both transmissive and reflective elements can be fabricated by using approprite LC, making them attractive as thin and light-weight optical elements in wearable devices [1]. On the other hand, the necessity of complex polarization patterns for fabrication and inherent dispersion, among other shortcomings pose challenges for widespread use of these functional optical elements. In this presentation, we present a structure that confers wavelength selectivity in the forward diffraction property towards suppression of achromatic dispersion in diffractive optical elements.