Glass, gel, or soft matter material near the phase transition point has high symmetry and various physical quantities are spatially uniform. Such uniformity is isotropic and highly transparent and has practically important and useful physical properties. On the contrary, high symmetry makes observation by structural analysis equipment such as microscopes and X-rays ineffective and is a major obstacle to material design and synthesis based on physical property measurement. Therefore, we recently found a new principle of a fluctuation microscope for observing dynamic inhomogeneities in soft matter and completed a prototype. In gel, glass and mixed or complex systems containing different species of molecules, cooperative dynamic modes appear hierarchically based on local molecular motion, even if they are liquid state without static material structure. appear. This fluctuation microscope directly visualizes the dynamic spatial inhomogeneity of such fluctuations in modes of collective motions.

White lasers are becoming increasingly relevant in various fields since they exhibit unprecedented properties in terms of beam brightness and intensity modulation. Here we show that in hybrid materials based on modified and/or dye-doped liquid crystals, white laser light can be effectively generated upon optical pumping. We demonstrate a multicolor stimulated emission phenomenon obtained in dye-doped, liquid crystalline systems or in a multifunctional phase-separation system based on polymer matrix encompassing liquid crystals and multiple organic chromophores, where the precise color adjustment can be provided by applying the external electric DC fields or pumping energy density. The use of liquid crystalline materials for laser light generation can bring several advantages, like better photostability comparing to polymeric lasers, easy tunability of emitted light, e.g., by applied of the electric field, low cost of fabrication, and multitude of randomly or precisely generated photonic structures, which can be controlled by the external fields.

Flexible electronic devices composed of polymers and elastomers require high mechanical durability to maintain their performance during cyclic bending. To design the appropriate structure for such devices, it is important to identify the position of a neutral mechanical plane (NMP) where there is no strain inside a bending material. In this study, the NMP position of bending polydimethylsiloxane (PDMS) film, which is a common soft material used in flexible electronic devices, is experimentally identified through internal strain measurement using a cholesteric liquid crystal sensor. Notably, the NMP of the bending PDMS film reversibly shifts toward the inner bending surface. Further, considering the NMP shifting enables us to fabricate a flexible electronic device with high mechanical durability. Quantifying the NMP position facilitates the development of device designs for flexible electronics.

We developed a unidirectionally aligned PDLC film with liquid crystal (LC) droplets permanently aligned along the film’s normal direction using the polymer stabilization method. Due to the unidirectional alignment of LC droplets, the aligned PDLC film shows selective scattering: it scatters light with a large incident angle but remains transparent for the small incident angles. We studied the selective scattering properties of aligned PDLC and optimized its electro-optical performance to use as a light efficiency enhancement film. The optimized aligned PDLC film increases the light efficiency of a Quantum Dot (QD) backlight film by about 20%. This aligned PDLC film can also improve the light efficiency of other flat panel displays like OPED, MLED, etc.

Side-chain engineering has been widely applied in organic electronics and liquid crystal science to control solubility, self-assembly, surface alignment, mesomorphism, and transition temperatures. However, the incorporation of flexible side-chains often complicates purification and lowers thermal stability and their nanosegregated areas of amorphous side-chains do not contribute to most optical and electronic properties of a mesophase. Herein, we report side-chain free liquid crystals that generate nematic and smectic mesophases and studied the influence of molecular properties on transition temperatures and mesophase structures. Molecular, optical and electronic properties are compared to analogous liquid crystals containing side-chains that display aggregation induced fluorescence.

Topological solitons relevant in different areas of physics are fascinating topologically protected localized perturbations of ordering fields. We combine experimental and theoretical approaches to demonstrate refraction, reflection, and lensing of weak laser beams by topological solitons appearing in frustrated cholesterics. One-dimensional twist walls and two-dimensional torons are controllably generated in thin films of unwounded cholesterics. We show how their interactions with light are well described using a generalization of Snell’s law and ray-tracing models. We conclude with the perspective that including high-intensity light (optical solitons) opens also optomechanical applications. All these findings will enhance the interest in optics and photonics of frustrated cholesterics.

By virtue of their constituents’ soft matter attributes and easy susceptibilities to applied fields, liquid crystalline chiral photonic crystals exhibit highly tunable linear and nonlinear optical properties that allow applications throughout a very wide spectrum. In particular, nearly-mm thick 1-D chiral photonic crystals fabricated with cholesteric liquid crystal are shown to be capable of polarization rotation and switching of complex laser vector fields with response times that can be as fast as sub-picoseconds, and operating wavelength ranging from the visible to near- and mid-IR range. [Ref.: Nature Comm. 8, Article number: 727 (2017); PNAS 2021, 118 (16)].

Photoalignment technology has attracted much attention from the viewpoint of noncontact patterning of large-area coatings. We report on direct alignment patterning in coatings by scanning wave photopolymerization of liquid crystals and nonlinear optical reorientation of dye-doped liquid crystals.

Ultrafast laser processing considerably gains in efficiency when using liquid crystal based spatial light modulators (LCSLM) to tailor the laser beam shape for upgradedsurface or bulk structuring.The fidelity of the experimental beam shape when compared to the target intensity distribution is of great importance for precise and controlled machining. Due to the physical characteristics of LCSLM, their non-perfect optical response has to be taken into account when designing phase masks. In this contribution, we'll discuss phase mask optimization for LCSLM for several beam shapes and present some applications in surface, bulk processing as well as in ophthalmology.

Optics manufacture is not easy – a piece of glass needs to be through water and fire, literally. And then more… It is even harsher for emerging metasurface technologies, involving solvents, developers, ion-etching, etc. The fourth generation optics (4G Optics), making feasible for thin planar films to be competitive with conventional optics in most applications and enabling performance features practically prohibited for other planar optics technologies that suffer from low efficiency, haze, and small area, it also is making a historical breakthrough in optics manufacturing by dramatically reducing its impact on environment along with time and cost. The 4G optics makes it possible a 1000x reduction of required material quantities compared to high quality optics of similar functionality, and at least a 1000x reduction of manufacture time, along with customization and reconfigurability of optical functions, and opportunities of recycling both the materials and substrates.

In this work we realize an optical resonator incorporating nematic liquid crystal in which photonic cavity modes are in strong light-matter coupling regime with excitons in a 2D organic-inorganic perovskite layer. Using electric field tunability provided by the liquid crystal we can bring our structure to the regime of Rashba-Dresselhaus spin orbit coupling. By a preparation of the orienting polymer layers within the cavity to break inversion symmetry of the liquid crystal layer we were able to engineer polariton energy band structure exhibiting locally non-zero photonic Berry curvature, which can be tuned by an external electric field.

We report the development of an optical element that can be dynamically switched between different modes of operation. Namely, it can produce parabolic wavefront and thus focus light, but, when wished, it can be switched into a conical or linear wavefronts producing thus tunable axicons or prisms. The element uses nematic liquid crystals and is based on a simple production technique making it suitable for high volume manufacturing. The basics of its operation as well as of its optical performance data will be reported.

We investigate a lyotropic mixture presenting in the calamitic nematic phase (NC) and its corresponding calamitic cholesteric phase (ChC), where a small amount of the chiral agent (brucine sulfate) was added. Different experimental techniques (polarized optical microscopy and laser conoscopy) were used to characterize the phases. The main technique employed in the analysis of the structure and local ordering at nanoscale is the Small-Angle X-ray Scattering, where advanced modeling analysis were applied. The lyotropic nematic mixtures was composed of potassium laurate/potassium sulfate/dodecanol/water and the cholesteric phases were obtained from these mixtures, by adding the chiral molecule, brucine sulfate. From an advanced modeling analysis, we show that the micellar overall shape is not modified by the doping with brucine. However, the presence of the brucine between micelles in the ChC phase imposes a higher correlation between micelles along the direction of the pseudo-lamellar ordering. Finally, the order parameter 〈P_2 〉 was calculated and these values for the phases NC and ChC are 0.8133(6) and 0.747(2), respectively, indicating a slightly higher orientational ordering in the NC phase.

An electrically tunable achromatic polarization rotator has been developed based on the hybrid splay-twist (HST) and hybrid-aligned super twist (HAST) liquid crystal. The continuous angular rotation, and achromatic operation across the entire visible spectrum. The tuning range of the polarization rotator is up to 90° or to 180° and the degree of linear polarization (DOLP) remains. Based on the HST-LC, the multi-functional smart glass is realized with light field, dimming and scattering control. This work provides possibilities in the design of optical systems and spatially polarization multiplexing elements. The designed smart glass provides novelties in smart (green) architecture.

With the help of augmented reality (AR) ) and virtual reality (VR) systems, users can receive information and connect with each other via near-eye displays (NEDs). However, several challenges still need to be addressed, especially the optics. Users wearing current NEDs typically suffer from vergence-accommodation conflict (VAC). Furthermore, people with refractive errors need a pair of prescription lenses to clearly see the virtual image and/or environment. Hence, VAC-free AR/VR systems with vision correction functions should be developed. Furthermore, the AR/VR systems must be designed with slim form factors. Liquid crystal (LC) optical elements with a thin form factor have been demonstrated for light modulation in versatile optical systems; thus, LC-based solutions have been proposed for AR/VR systems in the past decade. In this paper, we provide a comprehensive review on LC-based optical systems and suggest possible solutions how LC active optics could be used in NED systems. It focuses on the fundamental optics of NEDs, origins of VAC and current LC-based solutions, LC lenses for vision correction function, and the guidelines for solving the two aforementioned challenges using LC lenses. We also introduce some recent progress in our group.

The interaction of light beams with helical objects allows the emergency of the optical vortices. Understanding and manipulating the dynamics of helical defects can generate versatile sources of optical vortex beams. Using a magnetic ring, matter vortices can be trapped on a nematic liquid crystal cell. By applying a low-frequency voltage, we observe oscillatory rotating and beating matter vortices. Experimntally, we determine the region of parameters where the dancing vortices are observed. The amplitude equation allows describing the dancing vortices, which presents similar behaviors to those observed experimentally.

We present two novel multilayer active linear to circular polarizer designs where the sense of the polarization is controlled with a simple AC voltage bias. The designs employ liquid crystal that is electrically biased to control their index of refraction. Layers of periodic lattices deposited on glass carry a bias voltage that changes the delay through the liquid crystal and creates the desired polarization states. The structure is optimized using a multi-objective genetic algorithm approach. The assembly leverages silicon microbeads to maintain the liquid crystal thickness and the metal patterns fabricated using electron beam lithography. The work was performed in support of a DARPA contract.