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• 4-alcyloxy-2,3-difluorobenzoic acids self-associate as hydrogen-bonded SmC and SmA liquid crystals. • Mixing 4-alcyloxy-2,3-difluorobenzoic acids and 4-octyloxybenzoic acid the stabilizes a supplementary nematic phase. • The nematic phase shows a relaxation at 1.2 MHz frequency and a short response time to electric field in the millisecond range. [ABSTRACT FROM AUTHOR]

• Hyperpolarizability endorses HBTFLC is a potent candidate for NLO applications. • H-bonds inducing higher order sm F* & sm G* phase due to layered structure. • Less global hardness and high softness of HBTFLC evidenced to induced LC behaviour. • Tuneable LC with NLO properties is added advantage to stable HBTFLC complex. The current research work incorporates structural, experimental and computational studies of a hydrogen bond thermotropic ferroelectric liquid crystal (HBTFLC) complex synthesised from DL-tartaric acid (DLTA) and 4-heptyloxybenzoic acid (7OBA) with 1:1 ratio. Spectroscopic studies (XRD, NMR, FTIR, UV–Vis) and Density Functional Theory (DFT) are utilized to confirm intermolecular hydrogen bonds in the synthesised complex. Polarizing Optical Microscope (POM) study confirms the phase sequence (N*, Sm C*, Sm F* and Sm G*) while Differential Scanning Calorimetry (DSC) explore the thermal properties of the mesophases. The Frontier Molecular Orbital (FMO) and Molecular Electrostatic Potential (MEP) surface analysis also explore the donor-acceptor interactions, stability and chemical reactivity of the complex. The nature of H-bond is estimated by Natural Bond Orbital (NBO) studies with the support of Atom-in-Molecules (AIM) and Reduced Density Gradient (RDG) analysis. Nonlinear Optical (NLO) properties of the complex are studied by calculating its polarizability and hyperpolarizability. [Display omitted] [ABSTRACT FROM AUTHOR]

• Introduces polarization modulation in SIM to suppress background. • Enhances structural fidelity and resolution through multidirectional fusion. • Addresses key SIM limitations, improving signal localization and image quality. We report a structured illumination microscopy (SIM) reconstruction method based on polarization modulation (PM), which can suppress background noise by utilizing the polarization-sensitivity properties of fluorescent dipoles. The proposed method employs a ferroelectric liquid crystal (FLC) spatial light modulator (SLM) to generate multidirectional interference patterns, and uses a combination of two liquid crystal variable phase retarders (LCVRs) and a quarter-wave plate (QWP) for flexible and rapid polarization modulation. The results of simulations and experiments demonstrate that the combination of SIM and PM effectively suppresses background noise in SIM with a slight improvement in resolution. This technique also solves the problem of structural distortion that occasionally exists in SIM and improves the accuracy of the reconstruction. [ABSTRACT FROM AUTHOR]

• Detailed description and analysis of twisted domains in NF phase. • The first theoretical description of defects in ferroelectric nematic phase, NF. • Description of disclination lines. • Effect of the applied electric field on defect structure in a confined geometry. Ferroelectric nematics present properties promising for applications, which strongly depend on the confinement conditions and the presence of defects. In this work, we have observed and analysed textures in the cells with homogeneous geometry for a ferroelectric nematogen. The studied compound designated NF6 reveals the ferroelectric nematic phase, N F , directly on cooling from the isotropic phase. The N F phase is stable and persists down to the room temperatures. Textures in the homogeneous cell with antiparallel alignment prefer to be arranged in twisted domains with borderlines oriented preferentially in the perpendicular direction with respect to the surface alignment (rubbing direction). We have described these domains and developed a model of 2π disclinations, which are separating the areas with an opposite twist sense. We discuss the character of disclination charge and explained why these disclination lines prefer to be oriented perpendicularly to the rubbing direction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electrical vehicle safety using optical shuttering action. • A liquid crystal ingredient optical shutter is devised and characterized. • Optically shuttering action characteristics are discussed. • Compilation traditional devices indicates superior features of liquid crystal device. This intermediate phase between solid and liquid enables liquid crystal engineers for various interesting yet fascinating thermo-optical applications. One such application of exploited for electric vehicle safety is optical shutter realized using thermotropic liquid crystals. Optical shutters are essential components in various optical systems, in providing control over the transmission of visible light. These shutters are categorized into various types of mechanical shutters, electro-optical shutters, liquid crystal optical shutters (LCOS) etc. liquid crystal cells and polarizing elements to quickly change the transmittance of light, making them ultimate for applications such as imaging and precision illumination. In this work, we explored the experimental techniques, key specifications, features, and applications of an optical shutter developed using liquid crystalline material LCOS. [ABSTRACT FROM AUTHOR]

[Display omitted] • New chiral liquid crystals with ferroelectric features exhibit low melting points and a wide temperature range of the chiral smectic C* phase with a sub-micrometer helical pitch. • New chiral liquid crystals with ferroelectric features have a great potential for the deformed helix ferroelectric (DHF) mode. • Synthesized compounds could be used in fully integrated polarization-based photonic transducers with excellent linearity and the highest sensitivity observed in ferroelectric liquid crystals for DHF mode. • Synthesized compounds could be used in a new class of optical sensors for industrial monitoring networks and brain/machine interfaces with unprecedented performance. Nine compounds containing fluorine or chlorine atoms in the lateral position in the rigid core with a chiral terminal octyloxy-chain were synthesized mainly using Suzuki-Miyaura coupling, Mitsunobu, hydrogenation, and esterification reactions. New compounds were investigated using polarized optical microscopy (POM), differential scanning calorimetry (DSC), spectrophotometry, and electro-optical methods. A computational analysis of the effect of lateral substitution by halogen atoms on the phenyl ring on the dipole moment of the compound was provided and discussed. The designed compounds exhibit a wide temperature range of the ferroelectric phase (>40.0 °C), a low melting point (in most cases below 50.0 °C), low melting enthalpy (around 10.0–20.0 kJ/mol), a short helical pitch (in most cases below 200 nm at room temperature) and high tilt angle that ensures a cone angle of up to 90°; all those properties make them of great potential for the deformed helix ferroelectric (DHF) mode. Revealed features allow synthesized compounds in fully integrated polarization-based photonic transducers to have excellent linearity and the highest sensitivity observed in ferroelectric liquid crystals for DHF mode. For the first time, the DHF effect was reached for the single molecule FLC material in a broad temperature range down to 38 °C. These findings pave the way for a new class of optical sensors for, among others, industrial monitoring networks and brain/machine interfaces with unprecedented performance. [ABSTRACT FROM AUTHOR]

Electro-optic modulation based on a graphene nanoelectromechanical system (NEMS) with superlubricity is proposed and systematically theoretical investigated. We demonstrate that the superlubricity greatly improve the performance of photoelectric modulators based on graphene NEMS due to its extremely low coefficient of friction. The modulation voltage of graphene NEMS electro-optic modulation with superlubricity can be reduced to 200 mV, which is 1–3 orders of magnitude larger lower than that of the traditional electro-optical modulator, giving rise to a dramatic reduction of the power consumption of the modulator by approximately 3 orders of magnitude. The modulation response speed can reach nanoseconds, which is 4 orders of magnitude higher than the speed of traditional mechanical electro-optic modulation. At the same time, this modulator has a very wide modulation wavelength range and is not sensitive to the angle of incident light. Two-dimensional material devices, incorporated with mechanical modulation and superlubricity, will have important applications in optoelectronics and optical communication. Electro-optic modulation based on a graphene nanoelectromechanical system (NEMS) with superlubricity is proposed and systematically theoretical investigated. We demonstrate that the superlubricity greatly improve the performance of photoelectric modulators based on graphene NEMS due to its extremely low coefficient of friction. The modulation voltage of graphene NEMS electro-optic modulation with superlubricity can be reduced to 200 mV, which is 1–3 orders of magnitude larger lower than that of the traditional electro-optical modulator, giving rise to a dramatic reduction of the power consumption of the modulator by approximately 3 orders of magnitude. The modulation response speed can reach nanoseconds, which is 4 orders of magnitude higher than the speed of traditional mechanical electro-optic modulation. At the same time, this modulator has a very wide modulation wavelength range and is not sensitive to the angle of incident light. Two-dimensional material devices, incorporated with mechanical modulation and superlubricity, will have important applications in optoelectronics and optical communication. [Display omitted] [ABSTRACT FROM AUTHOR]

Materials with spontaneous polarization is very promising in valley electronics because of its potential application in encoding and storing information. In this paper, we proposed a stable two-dimensional ferromagnetic valley material H -ScAt 2 which can spontaneously generate valley splitting and exhibit intrinsic anomalous Hall effect. The valley polarization is 0.245 eV, which is large than most of the reported materials. The structural stability is verified by our phonon and molecular dynamic calculation. The Curie temperature of H -ScAt 2 monolayer is about 840 K, which is above room temperature. [Display omitted] • H-ScAt 2 exhibits anomalous valley Hall effect with huge valley polarization. • The spin direction is out of plane, and the Curie temperature is about 840 K. • The band gap could be significantly tuned by strain with steady valley polarization. [ABSTRACT FROM AUTHOR]

• Investigating non-mechanical axial focus tuning by coherent beam combining (CBC) technique. • The method does not depend on any made-to-order element to achieve axial focus tuning. • The influencing factors of the tunable range of focus are analyzed. • A method using tilt modulation to achieve larger range of focus tuning is proposed. • The proposed method will find its applications in the field of laser processing. High-speed variable-focus optics brings new opportunity to the applications of fiber laser in the fields of advanced laser processing, laser three-dimensional (3D) printing, imaging and so on. As an emerging field, variable- z -focus optical elements have been developed rapidly. There are many approaches to achieve high-speed variable focus such as ferroelectric liquid crystal lens, acoustically driven fluid lenses and enhanced adaptive optical technologies. In this paper, a method of non-mechanical axial focus tuning by coherent beam combining (CBC) technique is investigated. The method does not depend on any made-to-order element to achieve the high-speed variable focus. We provide detailed design processes and theoretical basis of how to achieve focus tuning by CBC technique. Then, the influencing factors of the tunable range of focus are analyzed. We also propose a tilt modulation assisted method in this paper to extend the tuning range furtherly. Finally, a visual demonstration is carried out by spatial light modulators to verify the method and achieving 10 cm tuning range of focus point. [ABSTRACT FROM AUTHOR]

The present work aims to use the Quantum Espresso software to theoretically investigate the spontaneous polarization and refractive indices of barium titanate (BaTiO 3) in its tetragonal phase, and their dependence on the considered DFT exchange-correlation functionals. Among the functionals implemented in Quantum Espresso, twenty-four functionals were considered. The calculations, in which pseudopotentials of type ultrasoft were used, show that the values of all studied magnitudes depend on the used exchange-correlation functional. According to the obtained results, for the considered functionals, it appears that there is a linearity between the spontaneous polarization and the ionic shift difference Δz(Ti)-Δz(O z); this linearity can be explained by the fact that the dipolar interaction Ti-O z is the main contributor to the spontaneous polarization, being seen that: (i) the spontaneous polarization is a consequence of the coupling between the displacements of the constituent ions and their effective charges, (ii) the ionic shifts lead to a decrease in the Ti-O z distance and an increase in the Ti-O x and Ti-O y distances, and then an increase in the Ti-O z dipolar interaction compared to the Ti-O x and Ti-O y dipolar interactions, and (iii) the Ti and O z ions possess the highest Born effective charges (in absolute values), in the polar direction, compared to the other ions, as reported in the literature. However, the closest values of the spontaneous polarization to the experimental data were obtained for the exchange-correlation functionals VDW-DF-C09, PZ, VDW-DF-CX, VDW-DF3-OPT1, VDW-DF2-C09, WC, and PBESOL. For these functionals, the refractive indices of ordinary and extraordinary polarizations were studied as a function of the light wavelength, in the range 160–940 nm. The obtained results show that the behavior of both refractive indices with respect to the wavelength, for visible light, is quit similar to that of Sellmeier equation with good agreement with the experimental data, particularly for the van der Waals functionals VDW-DF3-OPT1, VDW-DF-CX, VDW-DF2-C09, and VDW-DF-C09. [ABSTRACT FROM AUTHOR]

Domain switching is one of the essential contributions for strain in ferroelectric materials. In this work, we utilize anisotropic composition gradients (CGs) to induce anisotropic orientation of both defects and spontaneous dipoles, aiming to enhance the contribution of domain switching on strain in KTa 1– x Nb x O 3 single crystal. In this way, a remarkable improvement (over 60%) of strain is obtained in KTa 0.58 Nb 0.42 O 3 single crystal along the smallest CG direction, achieving a large unipolar strain, i.e. 0.29%, at low driving electric field 10 kV cm–1. It is attributed to the preferred orientation of both defects and spontaneous dipoles along the largest CG directions, then improving the contribution of domain switching on strain along the smallest CG direction. Particularly, owing to the existence of E in as recoverable forces caused by both flexoelectric fields and defects pinning effect, KTN show nearly zero remnant strain (s rem) along with the small CG directions, corresponding to the double P-E loops. Moreover, the V–PFM images confirm that CGs can influence the microdomain structures. Thus, designing special anisotropic CGs materials is expected to be a novel method to improve the strain properties and a potential way to flexibly design next-generation anisotropic piezoelectric materials. Composition Gradients (CGs) can significantly improve the contribution of domain switching on strain by inducing preferred orientation of spontaneous polarization and defect dipoles. It provides a novel method to design graded crystals to achieve strain properties enhancements. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Tetragonal-to-monoclinic Bi 4 Ti 3 O 12 (BIT) exhibits complicated domain patterns thanks to its two independently switchable spontaneous polarizations that lie in the ac plane of the monoclinic unit cell. Utilizing the nonlinear theory of ferroelectric phase transformation based on the deformation gradient tensor and spontaneous polarization, we systematically analyzed domain patterns in BIT, classifying its domain walls (DWs) into five different classes. Three-dimensional piezoresponse force microscopy (3D PFM) was then adopted to characterize the ceramic BIT, revealing intriguing domain patterns in planar, lateral , as well as tilted grains. Guided by the nonlinear theoretical analysis, 3D polarization distributions were successfully reconstructed, wherein 9°-, 90°-, 91°-, and 180°-DWs were observed along with 171°-charged DWs. The nonlinear analysis is thus confirmed by 3D PFM characterizations, and the combined theoretical analysis and experimental investigation contribute to our understanding on the 3D tetragonal-to-monoclinic ferroelectric domain patterns. Image, graphical abstract [ABSTRACT FROM AUTHOR]

We report the development of chiral smectic C (SmC*) ferroelectric liquid crystals (FLCs) obtained by mixing of a nematic liquid crystal (NLC) as a host and chiral non-mesogenic dopants. The NLC is a binary eutectic mixture of phenyl- and biphenyl-pyrimidines, while chiral dopants belong to homologous series of secondary dilactates with terphenyldicarboxylate core. The induction in the mixtures not only the cholesteric phase, but also the wide temperature range ferroelectric SmC* phase with the helix pitch p 0 ≈ 100 nm and the spontaneous polarization P s about 70 nC/cm2 has been confirmed by dielectric, optical, and electro-optical measurements. The developed FLC mixtures are highly efficient for the deformed helix ferroelectric liquid crystal electro-optical mode because the mixtures combine mechanical stability (or mechanical shock resistance) of NLCs and kilohertz switching frequency (due to short helix pitch) of FLCs. These FLCs can be used to create various photonic devices, such as generators of vortex light fields and field-sequential color displays. • Mixing a nematic matrix and non-mesogenic chiral dopants affords ferroelectric liquid crystals. • As chiral dopants, a homologous series of dilactates with terphenyl dicarboxylate core was synthesized. • Developed mixtures combine shock resistance and short response times (tens of microseconds) in DHF electro-optical mode. • Short helix pitch (ca. 100 nm) and broad temperature range (10 to 63 °C) were revealed for these new liquid crystals. • Impact of alkyl chain length in chiral dopant on electro-optical properties of ferroelectric liquid crystals was studied. [ABSTRACT FROM AUTHOR]

[Display omitted] • PCNPs were synthesized using magnolia champaca seed pods and studied their doping effect on the PDFLC properties. • FESEM image results indicate the spherical shape of PCNPs of particle size ∼27 nm. • Fluorescence spectra show an enhanced two-fold increase in emission intensity peak at 412 nm wavelength for 0.5 wt% PCNPs doped PDFLC. Herein, porous carbon nanoparticles (PCNPs) were synthesized using magnolia champaca seed pods and studied their doping effect on the polymer-dispersed ferroelectric liquid crystal (PDFLC) properties. The effect of PCNPs concentration (≤0.75 wt.%) on the morphology of PDFLC, polarization, and permittivity are investigated in thin sample cells. Field emission scanning electron microscope image results indicate the spherical shape of PCNPs of particle size ∼27 nm diameter. Temperature-dependent electro-optic and dielectric properties are also investigated in the wide SmC* phase and near transition temperature of SmC*-SmA*. Polarising optical microscope textures confirm the non-homogeneity of FLC molecules in the polymer matrix as a function of PCNPs concentration. The spontaneous polarization and anchoring energy coefficients increase with increasing the doping amount of PCNPs. The phase transition temperature is found unaffected by PCNP doping in all prepared samples. In PDFLC and PCNPs doped PDFLC composites, usual behaviour of permittivity as a function of temperature is observed. Fluorescence spectra show an enhanced two-fold increase in emission intensity peak at 412 nm wavelength for 0.5 wt.% PCNPs doped PDFLC while concentration-dependent quenching and slight redshift have been observed for the 0.75 wt.% PCNPs doped PDFLC. The enhanced electro-optic and dielectric properties observed in the composites suggest potential applications in displays, sensors, and optical devices. The findings open doors for further exploration and utilization of these functional materials in advanced electronic and photonic technologies. [ABSTRACT FROM AUTHOR]

Carrier-transporting ferroelectric liquid crystals consisting of quinquethiophene and lactic ester units were synthesized. One compound exhibited a chiral smectic C (SmC*) phase, and another compound exhibited a chiral smectic crystal phase at room temperature below the SmC* phase. The bulk photovoltaic effect was observed in the polarized chiral smectic crystal phase. The absorption edge was shifted to 570 nm from 500 nm of a terthiophene analogue, due to the extension of the π-conjugated unit. In the polarized smectic crystal phase doped with PCBM, the open circuit voltage and short circuit current was 0.72 V and 270 μAcm−2, respectively. The fill factor was improved to 0.63 and the power conversion efficiency was 0.7% in the PCBM-doped quinquethiophene derivative. The spectral sensitivity was extended to 700 nm, due to the absorption of PCBM as well as compound 1. Since compound 1 exhibits the SmC* phase above the chiral smectic crystal phase, the voltage for the poling treatment was remarkably reduced to 5 V from 40 V in the terthiophene analogue. [Display omitted] • Bulk photovoltaic effect in ferroelectric liquid crystals consisting of quinquethiophene and lactate units. • Extension of spectral sensitivity for the bulk photovoltaic effect by an extension of the π-conjugated unit. • Improvement of the fill factor of the bulk photovoltaic effect in the polarized smectic crystal phase. • Reduction of the poling voltage for the polarization of the chiral smectic crystal phase. [ABSTRACT FROM AUTHOR]

The recently discovered ferroelectric nematic liquid crystals have been reported to exhibit very large dielectric permittivity values. Here, we report a systematic investigation of the dielectric behavior of a prototypical ferroelectric nematogen by varying the thickness of the parallel capacitor measuring cell. While in the non-polar high temperature nematic phase results show only slight differences due to slight variations of the alignment, the measured permittivity values in the ferroelectric nematic phase show a linear dependence on the cell thickness. It is also shown that the characteristic relaxation frequency decreases inversely proportionally to the thickness. The results are discussed in terms of three different available models based on different underlying mechanisms, accounting for cancellation of the probe electric fields by polarization reorientation or by ionic charges, or based on a recently proposed continuous phenomenological model. • Measured dielectric permittivity values show a clear dependence on the thickness of the measuring parallel plate capacitor. • The characteristic relaxation frequency is inversely proportional to the sample thickness. • The obtained data have been analyzed in terms of three different models based on distinct physical mechanisms. [ABSTRACT FROM AUTHOR]

At high transmembrane electric field, a voltage sensitive ion channel is an insulator; when the field is critically reduced, it becomes a conductor of selected ions. The Channel Activation by Electrostatic Repulsion (CAbER) hypothesis proposes that an ordered polarization field of induced dipoles at the high electric field magnitude of the excitable state is overcome by thermal disorder at a critical depolarization. Increased repulsions between positive charges in the S4 segments cause an allosteric transition in which these segments expand and separate in a chiral proteinquake. The increased space allows the P segments to refold and the ion-semiconducting S5 and S6 segments to relax and expand outward in a breathing mode. Stripped permeant ions enter widened hydrogen bonds in the core helices of these segments. Driven by concentration differences and the electric field, the ions hop along transient pathways across the channel, appearing as fractal, stochastic bursts of single-channel currents. To support order amid thermal fluctuations, an object must be of a minimum size. The critical role of an ion channel's size suggests that the evolution of Metazoa became possible only after its DNA had grown enough to code for proteins larger than the correlation length. [Display omitted] • Branched sidechains are the link between depolarization and S4 movements. • Increased repulsions between positive charges drive the S4 segments apart. • As the pore-forming domain expands, its hydrogen bonds widen to become ion sites. • Permeant ions form fractal, stochastic bursts of current across the membrane. • Evolutionary gene doubling gave rise to large ordered phases of animal ion channels. [ABSTRACT FROM AUTHOR]

This paper describes theoretical and experimental studies for reducing ambient temperature dependence of KTN deflector by double-thermistor structure. A KTN deflector deflects transmitted beam by injecting electrons into KTN and applying voltage. The KTN chip is sandwiched between metal electrode blocks and electrically conductive graphite sheets. In the conventional structure, a thermistor for thermal control is attached to an electrode block. Low thermal resistance between the thermistor and a Peltier module induces ambient temperature dependence of KTN temperature despite thermal control. In the double-thermistor structure, the KTN temperature is controlled using the combined resistance of a thermistor attached to each electrode blocks and connected in series. We theoretically prove that a consistent KTN temperature can be maintained by controlling the value of the combined resistance. The errors of the series-connected thermistors are within ±0.02 °C when the temperature of the electrode block is 32 °C ± 1 °C. The average temperature of an accuracy of better than 1 °C was achieved when the temperature difference of electrodes is within 40 °C. The capacitance shift of KTN is decreased from 15% to 2% with this structure. Moreover, the deflection angle shift decreases from 4.3% to 1.6%. The difference between capacitance shift and deflection angle shift was considered to be due to temperature distribution and individual differences in each deflector used the experiments. • Double-thermistor structure reduced ambient temperature dependence of KTN deflector. • Resistance of series-connected thermistors is controlled in the structure. • The deflector temperature is controlled within ±0.02 °C when ambient is 32 °C ± 1 °C. • The errors of the series-connected thermistors are within ±0.02 °C when the temperature of the electrode block is 32 °C ± 1 °C. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we present a novel optical power splitter having an arbitrary split-ratio that can be tuned over a wide range by employing relatively low voltage levels. It is based on a slotted ring resonator. A 120 nm electro-optic polymer-filled slot is created throughout the circumference of the ring. The hybrid ring resonator is made to work between the full and off resonance states, allowing it to work as a power splitter. This is done by changing the refractive index of the electro-optic polymer inside the slot by the application of an external electric field. The splitter combines the electro-optic functionality of the polymer with the high index contrast of the silicon, resulting in a low tuning voltage power splitter. Over a small voltage range of 0–1 V, it is possible to change the split-ratio of this splitter from 0.031–16.738, making it 10 times better than other competing designs. In addition, it takes less than 500 ps to reconfigure the splitter. [ABSTRACT FROM AUTHOR]

The influence of the conformation state of the chiral component on the spontaneous polarization (P s) of multicomponent ferroelectric liquid crystal mixture was investigated using the molecular dynamics (MD) simulation method. It was demonstrated that the low-polarized conformational states of the chiral component was the most probable among all possible ones. The combination of the MD simulations and experimental measurements of liquid crystal mixture properties could be utilized to determine the conformation state of the chiral component dispersed in the ferroelectric liquid crystal mixture. • Spontaneous polarization of multicomponent FLC mixture depends of the conformation state of the chiral component. • Structural properties of FLC mixture depend on the conformation state of the chiral component. • MD simulation and electrooptic measurements can be used to identify the conformation state of the chiral component. [ABSTRACT FROM AUTHOR]

Self-assembling behaviour of a few lactic acid derivatives with several ester linkage groups in the molecular core has been studied. The molecular structure–physical property correlations has been discussed in the light of the temperature dependences of the static permittivity, dielectric anisotropy, spontaneous polarization, response time and torsional bulk viscosity for eight chiral ferroelectric liquid crystalline compounds. Depending on the molecular structure these compounds exhibit the chiral nematic (N*) phase, the paraelectric orthogonal smectic A* (SmA*) phase and the ferroelectric tilted smectic C*(SmC*) phase being thermally stable over relatively broad temperature range. The temperature behaviour of the spontaneous polarization clearly confirms the second order nature of the SmA*-SmC* phase transition and the first order nature of the N*-SmC* phase transition. The effect of temperature and molecular configuration on the polarization and on the dispersion anchoring energy coefficients has been established. The obtained results are discussed in order to contribute to the structure – property relationship for the specific class of soft organic materials which can be used for design of smart multifunctional liquid crystalline mixtures aimed for optoelectronic and photonic applications. • The structure–property correlations for eight chiral FLC's have been investigated. • The dielectric and electro optic properties have been reported. • Effect of molecular configuration on anchoring energy coefficients is established. • Low viscosity, large spontaneous polarization and low response times are observed. • The materials can be used for smart optoelectronic and photonic applications. [ABSTRACT FROM AUTHOR]

Abstract Design and studying of high-performance ferroelectric liquid crystal (FLC) materials targeted on high demand applications in display and photonic devices is described. Combination of high twisting ability with large spontaneous polarization (P S > 100 nC/cm2) resulted in promising FLC mixtures: almost defect-free alignment in electro-optical cells, the optical quality of the cells becomes comparable to that based on nematic liquid crystals, but switching is at least in order faster. The most important parameter is responsible for the remarkable performance of the materials is their ultra-short helix pitch as low as 65 nm. The key components of new mixtures provided the advanced properties are high-twisting diesters of terphenyldicarboxylic acid and chiral 1,1,1-trifluoroalkan-2-ols (FOTDA - n , n = 4–8). Analysis of origin of twisting power in SmC* phase, main difference with N* LC, relationship with chemical structure of chiral components are given. Thus, remarkable increase (up to 2.8-fold) of helical twisting power in the smectic C* (SmC*) phase upon lengthening of terminal alkyl chains from 4th to 8th homologues is observed for FOTDA - n . New chiral compounds, FOTDA - n , where n is 5 and higher, at concentrations as low as 25–33 mol.% in non-chiral BPP based SmC* host induce the helix pitch considerably below 100 nm. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

The temperature of the ZnTe detection crystal in a THz time-domain system was tuned continuously from 300 K to 1.5 K to minimize phonon absorption, thus enhance its detectivity. The THz peak amplitude was observed to increase more than 10 times. To explain this phenomenon, the THz transmission spectra of the ZnTe crystal at different temperatures were also measured, and the refractive index and absorption coefficient of the crystal were extracted. The experiments and theoretic analysis reveal that the significant detectivity enhancement is due to the reduced absorption of the THz field and phase matching change in the detection crystal with temperature decreasing, which makes the ZnTe crystal suitable for integrating with cryogenic applications. • A twelve-fold enhancement of the THz signal amplitude was observed when the ZnTe crystal was cooled from 300 K to 1.5 K. • THz detection sensitivity was calculated based on extracted refractive indices and absorption coefficients. • The significant enhancement is relevant to the suppressed phonon absorption. [ABSTRACT FROM AUTHOR]

Abstract Here we report the results of the dielectric and polarization measurements in the smectic and the tilted hexatic phases of a liquid crystal-nano composite consisting of commercially available ferroelectric liquid crystal (FLC) doped with the ZnO nanoparticles (NPs). It has been observed that the inclusion of NPs not only decreases in the transition temperature but also dielectric strength of the Goldstone mode without altering the associated relaxation frequency. An additional relaxation observed for the FLC-ZnO nanocomposite, but not present in the pure material is attributed to the manifestation of the primary director mode. The observed results are analyzed using the generalized Landau model to understand the effect of the coupling between the polarization and optical tilt angle. While there is no change in either the magnitude of the tilt or the polarization across the orthogonal to tilted smectic phase transitions, clear changes are seen for both the parameter across the transition to the hexatic phase. The FLC-ZnO nanocomposite exhibits decreased rotational viscosity and a faster response time, a feature attractive from an application point of view. Graphical abstract Unlabelled Image Highlights • The transition temperature of all the phase transitions decreases. • The strength of the GM is lowered, but not the associated relaxation frequency, and shows an additional relaxation. • There is no change in the tilt or the polarization across the orthogonal to tilted smectic phase transitions. • Clear changes are seen for the Ps and tilt across the transition to the hexatic phase. • There is a decrease in rotational viscosity and the faster response time. [ABSTRACT FROM AUTHOR]

Abstract Physical properties of new binary mixture of two ferroelectric liquid crystalline compounds, regarding the properties of the components, were studied. It turned out that both components and the mixture exhibit the ferroelectric smectic C* phase in a wide temperature range. Moreover, the calorimetric, texture observations as well as dielectric studies revealed an additional monotropic liquid crystalline phase for one of the mixture component, which was identified, based on X–ray diffraction results, as tilted one with hexagonal order within the layers. Dielectric spectroscopy has shown the strong low frequency relaxation process in the SmC* identified as related to Goldstone mode based on the mean–field model. Additionally, the molecular reorientation around the short axis was recognized in the monotropic hexatic phase. The temperature dependencies of the spontaneous polarization and switching time for new binary mixture and its components were compared and analyzed in terms for possible applications. Graphical abstract Unlabelled Image Highlights • Orienting polymer layer influence on molecular dynamics is studied by FDDS. • X-ray diffraction for identification of liquid crystalline phases is used. • DSC and POM was used to study thermal stability. • Parameters important for applications are designed. [ABSTRACT FROM AUTHOR]

Abstract Stable colloids in ferroelectric liquid crystal (FLC) of fine ferromagnetic CoFe 2 O 4 nanoparticles (NPs) coated with specially designed promesogenic ligands were obtained. The studying of FLC properties for these nanocomposite materials revealed significant changes in dielectric spectra and increase in rotational viscosity of FLC accompanied with noticeable degradation of texture. The changes in dielectric parameters have a pronounced NPs concentration dependence although it was shown that the cell surface contribute to these changes significantly, thus, the role of NPs in changing of the properties was critically revised. Monitoring of dielectric properties and other physical parameters of FLC with time confirmed a high stability of the material upon storage. The influence of magnetic field on basic parameters of FLC in NPs-FLC colloids was examined and explained taking into account highly developed and strongly interacting with LCs organic shell on the NPs surface. Despite a high stability and homogeneity of the composites, in magnetic field the materials do not reveal any significant changes from properties of pure FLC except of increase in viscosity which as a result of alignment of magnetic NPs along with magnetic field and strong interpenetration of LC molecules and NPs ligands. Highlights • Stable colloids of ferromagnetic nanoparticles in a FLC are prepared. • The nanoparticles are stabilized with dendritic promesogenic ligands. • Dielectric properties and FLC parameters are studied for the hybrid material. • The influence of magnetic field on the properties of the nanocomposites was examined. • The viscosity of hybrid material is sensitive to external magnetic field. [ABSTRACT FROM AUTHOR]

Abstract We study electro-optic properties of subwavelength-pitch deformed-helix ferroelectric liquid crystals (DHFLC) illuminated with partially polarized light. Theoretical results on the orientational Kerr effect and the modes of operation of such DHFLC cells are reviewed. By using the interferometry based approach to mixed-state geometric phases, we deduce the expressions for the total Pancharatnam and geometric phases of a partially polarized light wave passed through the DHFLC cell. We examine the effects of the polarization parameters on electric field dependence of the phases. Highlights • Electro-optics of deformed helix ferroelectric liquid crystals (DHFLCs) is reviewed. • The transfer matrix method is applied to model the transmissive and reflective modes. • Theory of modulation of partially polarized incident light in DHFLCs is developed. • The Pancharatnam and geometric phases of modulated light are computed. • The phases of non-unitarily evolving mixed polarization states are analyzed. [ABSTRACT FROM AUTHOR]

There are a series of polyimide material synthesized and studied with different dianhydride and diamine structures. By exploring the structural variations of these materials and their surface energy characteristics, we successfully obtained ferroelectric liquid crystal devices exhibiting exceptional optical and electrical properties. Notably, our findings highlight that a specific polyimide material comprised of dianhydride with a benzene ring structure and diamine with a long-chain amino structure demonstrates remarkable achievements, including a maximum contrast of 872 and a rapid response speed of less than 0.1 ms. These results establish the superiority of this particular polyimide material over its commercially available counterparts. Additionally, the optical characteristics of various polyimide materials were examined by establishing a correlation between these properties and the surface energy of the materials. This research presents a novel approach to developing alignment materials suitable for ferroelectric liquid crystal applications. The implications of our findings are of great significance in driving advancements in field-sequential-color display devices with high pixels per inch in the ferroelectric liquid crystal field. The FLC cells containing optimized polyimide (PI) composed of dianhydride and diamine structural components exhibit outstanding optical contrast and response speed. [Display omitted] • Polyimide (PI) materials with different dianhydride and diamine structures have been synthesized and studied. • FLC devices based on optimized PI display excellent contrast ratio of 872 and a rapid response speed of less than 0.1 ms. • The optimized PI material has been successfully implemented in the LCD Generation 4.5 mass production line. [ABSTRACT FROM AUTHOR]

In the present work, we study the structural, electrical and optical properties of barium titanate (BaTiO 3) and lead titanate (PbTiO 3) using the plane wave pseudopotential method and the PBESOL approximation in the framework of density functional theory (DFT). We use the open-source program Quantum Espresso to perform the calculation of optimized lattice parameters, spontaneous polarization and refractive indices of tetragonal BaTiO 3 and PbTiO 3 single crystals. In the calculations, all types of pseudopotentials were considered: ultrasoft pseudopotentials (USPP), norm-conserving pseudopotentials (NCPP) and projector-augmented wave (PAW). The calculated values of the optimized lattice parameters, the spontaneous polarization and the refractive indices of the tetragonal BaTiO 3 and PbTiO 3 show a good agreement with the experimental values, especially for the USPP and PAW pseudopotentials. [ABSTRACT FROM AUTHOR]

• Focused irradiation of ferroelectric crystals allows controlling the ejection of fluid jets from ferroelectric droplets. • The ejected jets can be walked by light over long distances on the ferroelectric solid substrate. • By reverting the substrate side, jets become thinner and exhibit the tendency of being repelled by the light spot. • Light induced splitting of fluid jets, jets redirection and jet's elongation opposite to the light spot, are observed. We report on the optical control of the recently observed electromechanical instability of ferroelectric liquid droplets exposed to the photovoltaic field of a lithium niobate ferroelectric crystal substrate. The ferroelectric liquid is a nematic liquid crystal in which almost complete polar ordering of the molecular dipoles generates an internal macroscopic polarization locally collinear to the mean molecular long axis. Upon entering the ferroelectric phase, droplets irradiated by unfocused beam undergo an electromechanical instability and disintegrate by the explosive emission of fluid jets. We show here that the regions of jets emission can be controlled by focusing the light beam in areas close to the droplet's edge. Once emitted, the fluid jets can be walked by moving the beam up to millimeter distance from the mother droplet. Reverting the lithium niobate substrate, jets become thinner and show the tendency of being repelled by the beam instead of being attracted, thus offering an additional tool for their optical manipulation. These observations may pave the way to intriguing applications of ferroelectric nematic fluids related to manipulation, actuation, and control of soft, flexible materials. [ABSTRACT FROM AUTHOR]

The electrical properties and effect of illumination on the photodetection properties were investigated for the fabricated device with Ru(II)-pydim complex interface layer. The Ru(II)-pydim interface was deposited by spin coating technique on a p-silicon substrate. The electrical and optoelectrical parameters of photodiode were analyzed via the current-voltage (I–V), capacitance/conductance-voltage (C/G-V) measurements under dark and different illumination power. The fabricated device has good electrical parameters such as the rectification ratio of 2.726 × 104, the ideality factor of 1.328, and barrier height of 0.805 eV under the dark condition. The current values of the device with Ru(II)-pydim interface at reverse bias were strongly dependent on the illumination intensities, confirming its photoconduction behavior. The I–V measurements under different solar illuminations present that the electro-optic device with Ru(II)-pydim complex as an interface has good photodiode parameters with the responsivity of 131 mA/W, and the detectivity of 1.63 × 1011 Jones at 100 mW/cm2. The photo transient measurements demonstrate that the Ru(II)-pydim complex based photodiode presents the desired photo-switching property. Therefore, the prepared Ru(II)-pydim based device can be used for electro-optic and photonic applications, particularly in the rapidly developing organic material-based device industry. • For the first time, Ru(II)-pydim complex was used in the photodiode application. • The device exhibits sharp photoswitching behavior between the high and low conducting state. • The device can be used for electro-optic and photonic applications in organic material-based device industry. [ABSTRACT FROM AUTHOR]

A new class of hydrogen bonded ferroelectric liquid crystals (HBFLC) have been designed and synthesized by intermolecular hydrogen bonds between mesogenic 4-decyloxybenzoic acid (10OBA) and non-mesogenic (R)-(+)-Methylsuccinic acid (MSA) which have been confirmed through experimental and theoretical studies. Further, Mulliken population analysis clearly reveals that the existence of hydrogen bonds, strength and dynamic properties. Textural observation and its corresponding enthalpy values are analyzed by polarizing optical microscope (POM) and differential scanning calorimetry (DSC) respectively. Paramorphic changes in Sm C* phase due to the change of refractive index, which clearly reveal that the complex could be used for filtering action in photonic devices. The transition from lone pair to π* with large stabilization energy evidently exposes the chiral phases in the present HBFLC complex. Intermolecular interaction is analyzed by using natural bond orbital (NBO) studies. The highest energy in the HOMO-LUMO shows the stable phase in the HBFLC complex. Molecular structure of the HBFLC complex possesses the monoclinic which has been evinced through x-ray analysis. The randomly oriented bunch of homogeneous molecules in Sm A* phase of the HBFLC complex is reported. [ABSTRACT FROM AUTHOR]

The influence of spherical zinc oxide nanoparticles (ZnO-NPs) incorporated in low concentrations (0.45, 0.7, 1.0 wt/wt%) into a polymer confined ferroelectric liquid crystal (FLC) has been investigated. Varying the concentration of ZnO-NPs is found to have a profound impact on the morphology of the polymer dispersed ferroelectric liquid crystal (PDFLC) composites. With increasing ZnO-NP content, the real and imaginary parts of the permittivity and the dielectric strength of a relevant relaxation mode depict an increase. However, the associated relaxation frequency shifts to lower values; a concomitant increase in spontaneous polarization is also observed. The response time of the composites slightly improved on doping with the ZnO-NPs. The changes in electro-optic and dielectric parameters are explained in terms of change in elastic energy as well as surface morphology of the composites. Interestingly, the polymer/liquid crystal environment is also seen to enhance the photoluminescence response of confined FLC. [ABSTRACT FROM AUTHOR]

Starting from a Langevin formulation of a thermally perturbed nonlinear elastic model of the ferroelectric smectic-C * (SmC*) liquid crystals in the presence of an electric field, this article characterizes the hitherto unexplored dynamical phase transition from a thermo-electrically forced ferroelectric SmC * phase to a chiral nematic liquid crystalline phase and vice versa. The theoretical analysis is based on a combination of dynamic renormalization (DRG) and numerical simulation of the emergent model. While the DRG architecture predicts a generic transition to the Kardar-Parisi-Zhang (KPZ) universality class at dynamic equilibrium, in agreement with recent experiments, the numerical simulations of the model show simultaneous existence of two phases, one a subdiffusive (SD) phase characterized by a dynamical exponent value of 1, and the other a KPZ phase, characterized by a dynamical exponent value of 1.5. The SD phase flows over to the KPZ phase with increased external forcing, offering a new universality paradigm, hitherto unexplored in the context of ferroelectric liquid crystals. [ABSTRACT FROM AUTHOR]

The present article deals with the interaction of octadecylamine (ODA) capped cadmium selenide quantum dots (CdSe QDs) and two ferroelectric liquid crystals (FLCs) having different values of spontaneous polarization (Ps). The pristine FLCs and FLC-QDs composites have been investigated by using steady-state and time-resolved fluorescence spectroscopic techniques. Stokes shift and the preferred alignment of FLC molecules in the presence of QDs are found to depend on the secondary order parameter of FLCs (i.e. Ps). The secondary fluorescence emissions have been strongly influenced by the concentration of QDs. The Förster resonance energy Transfer (FRET) was absent in both the composites. This article discloses the role of various factors, like relative orientation, dipolar interaction between donor and acceptor and the proximity of QDs (>10 nm), which might be responsible for the absence of FRET. FLC-QDs composites do not form a new class of luminescent material though the fluorescence properties of host FLCs are tailored in the presence of QDs by means of the change in molecular alignment. The change in lifetimes of FLC-QDs composites has not been observed. [ABSTRACT FROM AUTHOR]

• Spontaneous polarization and thermal conductivity are correlated in ferroelectric HfO 2 due to the lattice anharmonicity. • Pressures and compressive strains increase the spontaneous polarization and thermal conductivity in ferroelectric HfO 2. • Both the spontaneous polarization and thermal conductivity decrease with rising temperature in ferroelectric HfO 2. • Thermal conductivity in thin-film ferroelectric HfO 2 is significantly decreased when the thickness is less than 10 µm. The ferroelectric phase of hafnia (ferroelectric HfO 2) has been considered as a promising ferroelectric material for nanoscale electronic devices due to its robust ferroelectricity that is characterized by an electric-field-switchable spontaneous polarization. A perhaps long overlooked and hence rarely explored property in ferroelectric HfO 2 is the thermal conduction, which plays an important role in the thermal management and thermal stability of related ferroelectric devices. Both the spontaneous polarization and thermal conduction are intimately related to the lattice anharmonicity. It is hence natural to expect a correlation between the two quantities. In this work, we use efficient tailoring strategies such as pressure and strain engineering to investigate such a correlation. The calculated thermal conductivity of ferroelectric HfO 2 is 14.1 W m−1 K−1 at room temperature. We find that indeed the spontaneous polarization and thermal conductivity are positively correlated under pressure or strain in ferroelectric HfO 2 , namely the larger the spontaneous polarization, the larger the thermal conductivity, regardless of whether the spontaneous polarization or thermal conductivity is enhanced or suppressed. This is attributed to the dominant role of lattice anharmonicity, i.e., under a hydrostatic pressure or a compressive strain, the lattice becomes increasingly harmonic with an enhanced spontaneous polarization, facilitating the thermal transport. We further demonstrate such a correlation in three other representative ferroelectrics (i.e., tetragonal PbTiO 3 , wurtzite AlN, and hexagonal ABC ferroelectric LiBeSb), indicating that this may be a universal feature. The positive correlation between spontaneous polarization and thermal conductivity is further corroborated by their concurrent reductions with rising temperature. This work paves the way to establish the structure-property relation in ferroelectric HfO 2 and may offer novel avenues for the designs and applications of ferroelectric materials. [ABSTRACT FROM AUTHOR]

In the present study, the concentration-dependent dielectric, electro-optical, and electrochemical properties of ZnCdTeS quantum dots (QDs) doped E7 nematic liquid crystal (NLC) mixtures were investigated. The dielectric permittivity components (ε ‖ and ϵ ꓕ) and dielectric anisotropy (Δϵ = ε ‖ ˗ ϵꓕ) of NLC samples containing varied concentrations of ZnCdTeS QDs (i. e. 0.10, 0.25, 0.50, 0.75, and 1 wt%) were measured at various temperatures. In the nematic phase, the results demonstrated that ε ‖ increases much more than ϵ ꓕ upon an increase in the concentration of ZnCdTeS QDs. Δϵ enhanced as the concentration of QDs increased, reaching a maximum at 0.50 wt%, then decreased with further addition. Dielectric measurements revealed the formation of self-aligned QD arrays along the nematic director, which act similarly to multiple parallel capacitors in the NLC system. Moreover, electro-optical studies illustrated the significant effect of QDs doping on lowering the threshold voltage and response time. Interestingly, the optical switching-off time of NLC containing 0.50 wt% of the QDs decreased by ∼50% compared to that of the pure E7 sample. The reduced screening effect resulting from the QDs ion-capturing mechanism, enhanced effective intermolecular interactions, and increased dielectric anisotropy in the NLC system are the major factors responsible for the improved electro-optical characteristics. The impedance behavior of NLC cells was studied in the frequency range of 0.1 Hz–100 kHz. It indicated that the addition of ZnCdTeS QDs results in a remarkable increase of 96% in the electrical conductivity of the NLC system. Furthermore, the QDs doping significantly improved the NLC device's charge capacitance. Such studies would undoubtedly be beneficial for designing next-generation tunable optoelectronic systems since QDs can be utilized for tuning the dielectric anisotropy, electro-optical characteristics, charge capacitance, and conductivity of NLCs. [Display omitted] • The effect of ZnCdTeS QDs on the electro-optic switching, dielectric, and electrochemical features of E7 NLC was investigated. • The QDs doping considerably increased the dielectric anisotropy of the NLC. • Dielectric measurements demonstrated the creation of self-organized QD arrays along the nematic director. • The addition of QDs lowered the threshold voltage and response time of the NLC significantly. • The electrical conductivity and capacitance of the NLC were enhanced remarkably by addition of QDs. [ABSTRACT FROM AUTHOR]

• Wide band dielectric spectroscopy study of ferroelectric nematic material. • Dielectric study of both planar-aligned and homeotropic aligned cells. • The analysis of the Data in terms of three relaxation processes. • Mid frequency mode - dynamics of the correlated molecules in nematic phases. • Highest frequency mode – amplitude mode in the N phases which transforms to the phason mode in N F phase. A non-chiral ferroelectric nematic compound with a 1,3-dioxane unit in the mesogenic core called 2,3′,4′,5′-tetrafluoro-[1,1′-biphenyl]-4-yl 2,6-difluoro-4-(5-propyl-1,3-dioxan-2-yl) benzoate (DIO) was studied by dielectric spectroscopy in the frequency range 0.1 Hz–10 MHz over a wide range of temperatures. The compound exhibits three nematic phases on cooling from the isotropic phase, i.e., the ordinary paraelectric nematic N; the intermediate nematic N X and the ferroelectric N F phase. The least frequency process is due to the dynamics of ions. The middle frequency relaxation process P 1 is like as observed in other ferronematic compounds and this mode is a continuation of the molecular flip-flop motion in the isotropic phase to the collective dynamics of dipoles which are strongly coupled with the splay fluctuations in nematic phases. In addition to this process, DIO shows an additional collective relaxation process P 2 at higher frequencies both in the N and the N X phases. This mode originates from the polar/chiral domains of the opposite chirality, these arise from the spontaneous symmetry breaking of achiral mesogens in the N phase. Both collective processes, P 1 and P 2 , show soft mode-like characteristic behavior on cooling from the N to the N X -N F phase transition temperature and are shown to contribute independently to the formation of the ferronematic N F phase. [ABSTRACT FROM AUTHOR]

In this work, we have considered the application of thermodynamic model, as developed by us, to investigate, under electric field, the variation of relative temperature(T − T c ), where T c represents Sm C* − Sm A* transition temperature, and spontaneous polarization with tilt angle of Sm C* phase near Sm A* − Sm C* phase transition in surface stabilized ferroelectric liquid crystals (SSFLCs). Based on the concept of Landau-de-Gennes formalism, the free-energy density of the system has been written as an expansion series in powers of relevant order parameters and their coupling terms. Adopting usual method, we have evaluated the values of spontaneous polarization ( P s ) and relative temperature (T − T c ) as a function of tilt angle for seven SSFLCs materials. In case of materials exhibiting second-order transition a wide temperature variation in the tilt angle has clearly been observed. For materials showings first-order transition, the transition enthalpy has been found to be directly related to the Landu coefficient (b) associated with cubic power of orientational order parameter. We have found a close agreement between theory and experiment. [ABSTRACT FROM AUTHOR]

In the present study, the effect of dispersing Octadecylamine capped Cadmium Telluride quantum dots (CdTe QDs) on the memory behaviour, physical parameters and dielectric relaxations of ferroelectric liquid crystal (FLC) W-327 with the variation of dopant concentration and applied voltage has been examined. Significant changes have been observed in visible light absorbance, photoluminescence (PL), spontaneous polarization, optical response and relative permittivity of the FLC material with the addition of QDs. An average of 19% (Mix.1) and 28% (Mix.2) fastening of optical response in QDs dispersed FLC mixtures was one of the remarkable findings. Enhancement in visible absorbance along with the quenching in PL intensity has also been noticed in FLC/QD mixtures in comparison to pure FLC. The study of tan δ curves confirms the reduction of ionic impurities in the presence of QDs. Pure FLC as well as FLC/QD mixtures show time dependent memory effects. The memory behaviour of mixtures significantly depends upon the concentration of dopant CdTe. The memory effect was confirmed with the help of dielectric spectroscopy, polarizing optical micrographs and electro-optical study. The observed memory effect has been attributed to minimization of the depolarization field and ionic charges. The QDs dispersed FLC plays a major role to enhance memory effects by trapping the impurity ions under the application of bias voltage. These studies would be helpful to provide an idea for ionic impurity free memory devices having micro-second optical response and in security coded transmission. [ABSTRACT FROM AUTHOR]

In laser projectors, speckle reduction can be achieved by projecting a changing binary phase diffuser onto the screen. Here, we sequentially encoded a commercialized ferroelectric liquid crystal spatial light modulator (FLC-SLM) with the rows of a two-level orthogonal array of order sixty-four, thus obtaining a changing binary phase diffuser. With the help of this binary phase diffuser, the subjective speckle contrast ratio on the screen is reduced from C b =0.71 to C a =0.1. Based on the experimental results, a simplified transparent FLC-SLM design is first proposed. This newly designed FLC-SLM has two phase modulation depths and can be driven with the passive matrix addressing scheme. Therefore, the control electronics of the proposed FLC-SLM can be significantly simplified compared to the currently used one. [ABSTRACT FROM AUTHOR]

New binary mixture of thermotropic liquid crystalline compounds, possessing both ferro– and antiferroelectric smectic C* phases, has been studied by complementary methods: calorimetric, X–ray powder diffractometry and electro-optic. Additionally, quantum–chemical model based on the density functional theory was also applied. It was found that mixture studied did not exhibit antiferroelectric phase at any rate of heating or cooling in contradiction to its ingredients. On the other hand it has a wide temperature range of ferroelectric smectic C* phase, which is invariant with respect to different heating and cooling rates within the range of thermal hysteresis. Furthermore, temperature dependence of switching time and spontaneous polarization were measured. [ABSTRACT FROM AUTHOR]

• Cole-Cole diagrams, Smith Chat and the equivalent RC circuit were determined. • The capacitive and magnetic properties of the system were investigated in detail. • Fluctuating and self-consistent results for UV-spectra of the samples were obtained. Rosehip seed (RS) extract-loaded hydrogel samples RS1 (poly(AMPS-co-MBAAm), RS2 (poly(AMPS- co - CrA- co - MBAAm)), RS3 (poly(AMPS - co - MAA - co - MBAAm)) and RS4 (poly(AMPS -co - IA - co- MBAAm)) were prepared to examine their structural and optical properties. Furthermore, frequency and bias voltage evolution of dielectric and electrical parameters were analyzed using impedance spectroscopy (IS) for all samples at room temperature (RT). Fluctuating and self-consistent results were obtained in the Ultraviolet–visible (UV) spectrum of the samples. The conductivity mechanisms were determined by calculating the s parameters of all samples for different regions. The complex impedance, capacitance, phase angles, dielectric constant, tangent factor, electric modulus, and frequency variation of ionic conductivity for the rosehip seed loaded hydrogel were successfully analyzed in detail using IS in the broadband frequency range. The increase in ionic conductivity of the RS-doped hydrogel with increasing frequency was attributed to its ability to exhibit the Langevin equivalent of Brownian motion in viscoelastic fluids, surface/bulk Maxwellian stress relaxation behavior, and the validity of the Stokes-Einstein relationship in biological fluids. In particular, the capacitive effect observed as a result of the Cole-Cole diagrams of the dielectric constant adapting to Smith Chat and the equivalent RC circuit allowed the material to be used as a capacitor. (a) Dielectric constant plane plots and their circles on (b) the Smith chart for all samples. [Display omitted] [ABSTRACT FROM AUTHOR]

A novel optical beam deflector based on a Lithium niobate (LN) waveguide is demonstrated, which can operate at both electro-optic and thermo-optic modes. At the electro-optic mode, the microstructured serrated electrodes induce inhomogeneous change in the refraction index of LN waveguide via the Pockels effect when a voltage is applied. The incident beam is thus deflected with the deflected distance changing linearly with the applied voltage. A high deflection speed up to 2.5 GHz is observed experimentally. The optical beam deflector can operate at the thermo-optic mode, where the deflected distance depends on the applied electric power; thus it varies quadratically with the applied voltage. The deflection capacity at the thermo-optic mode is much higher than electro-optic mode, since the deflection distances are respectively 27.19 and 2.53 μ m for the thermo-optic and electro-optic modes at a 4 V applied voltage. Therefore, the distinct electro-optic and thermo-optic operating modes enable the LN optical beam deflector to be qualified for various tasks, such as optical scanning, optical modulator. • Both the electro-optic and thermo-optic operating modes are demonstrated for the Lithium niobate optical beam deflectors. • A high deflection speed up to 2.5 GHz is observed experimentally with an extinction ratio of 1.96 dB. • The thermo-optic mode has a high deflection capacity with a deflection distance of 27.19 μ m under a 4V applied voltage. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthetic methods of new orthoconic antiferroelectric liquid crystals (OAFLCs) are outlined. • OAFLCs with phenyl biphenylate rigid core exhibit several benefits compared to their analogues. • Cyclohexyl ring at the end of the chiral terminal chain increases and stabilizes the helical pitch. • The knowledge gained will help to design new OAFLCs mixtures for working electro-optical devices. Our recent advances on polymer-stabilised orthoconic antiferroelectric liquid crystals (PSOAFLCs) eliminated the asymmetry of switching times in electro-optical effect based on surface stabilized OAFLCs and paved the way for their effective use in many photonic and optoelectronic devices requiring very fast switching. To fabricate new modifications of PSOAFLCs, besides bi- and tetrafunctional monomers, multicomponent AFLCs mixtures with a very low meting point, high stability of the antiferroelectric phase at lower temperatures and higher helical pitch length are desirable. Herein, a very convenient synthetic method of new AFLC compounds with a phenyl biphenylcarboxylate structure of the rigid core with different length and shape of terminal chains is reported. The resulting mesomorphic properties and helical parameters are compared with those of analogues with a biphenyl benzoate structure of the rigid core. The designed AFLC compounds clearly possess definite advantages. Specifically, they exhibit lower meting points, higher clearing points, broader temperature range of the antiferroelectric phase (SmC A *) and much longer helical pitch length, especially for analogues with the shortest achiral terminal chain, but unexpectedly lower tendency to give the direct transition between the antiferroelectric and isotropic phase. The introduction of the cycloalkyl ring at the end of the chiral terminal chain increases the melting points, flattens the temperature dependence of the helical pitch and changes the sense of the helical twist, but also enhances the ability of the direct SmC A *-Iso phase transition, regardless the type of the rigid core. The obtained results highlight a possibility of utilizing compounds with the phenyl biphenylcarboxylate structure of the rigid core, designed under this work, together with previously prepared compounds with the biphenyl benzoate rigid core to formulate multicomponent OALFC mixtures with a very low melting point and a very high helical pitch length. [ABSTRACT FROM AUTHOR]

[Display omitted] • Supersaturation of cholesterol into ferroelectric liquid crystal revealed needles. • Needles aligned along the smectic layers and reduces the dielectric constant. • In SmA* phase, focal conic domains formation instead of needles. • Enhanced chirality level of the composite is realized in chiral nematic phase. We report the crystallization of cholesterol (concentration in ethanol 100, 200, 300, and 400 mg / dl) in combination with ferroelectric liquid crystal (FLC) in the form of cholesterol needles. This has been investigated by dielectric spectroscopy, Raman spectroscopy, and texture analysis through optical micrographs. The foremost impression of adding cholesterol is observed with a reduction in the relative dielectric permittivity value and ferroelectric (chiral smectic C, SmC∗) to paraelectric (chiral smectic A, SmA∗) phase transition temperature with increasing concentration of cholesterol in FLC. In higher concentrations of 300 and 400 mg / dl , crystallized needles have been observed as a result of the supersaturation state of cholesterol in FLC matrix. Texture analysis has revealed that these needles are optically birefringent. Elongation of needles is found to be perpendicular to the FLC molecular director, and hence parallel to the smectic layers also. Temperature dependent investigation has shown that cholesterol-based needles disappear gradually with temperature and has not been observed in nematic and isotropic phases of the material. The results have confirmed that the lines are not only the supersaturation of cholesterol only but it is the composition of both cholesterol and FLC material. This is because when these needles disappear in SmA∗ phase the focal conic domains appear there. The understanding of the behavior of the cholesterol addition on the properties of FLC could be helpful in exploring the possibilities of using FLC as a sensing element in the biosensing of cholesterol and other molecules. [ABSTRACT FROM AUTHOR]

A room-temperature antiferroelectric liquid crystal (AFLC) mixture has been prepared by doping two chiral fluorinated compounds into a four-component achiral phenyl pyrimidine-based host matrix. The suitability of the mixture for practical applications has been tested by optical polarizing microscopy, synchrotron X-ray diffraction, frequency-dependent dielectric, and electro-optic studies. The mixture possesses an antiferroelectric phase over a wide temperature range (nearly 82 °C) followed by a paraelectric phase for 13.7 °C. It is found to display very fast switching between 243 and 45 μs at the driving voltage of 3.2 V/μm in the SmC* A phase. At 20 °C, the mixture exhibits a moderately high spontaneous polarization (137 nC/cm2), low viscosity (1.01 Pa s) and fast switching (240μs). The formulated mixture is thus expected to be suitable for use in fast-response AFLC-based display devices. [Display omitted] • A wide range (nearly 82°) room temperature AFLC mixture has been prepared. • The mixture consists of two fluorinated chiral dopants and a phenyl pyrimidine achiral host matrix. • Its tilt behaviour is nearly orthoconic. • It exhibits moderately high spontaneous polarization and low viscosity. • At 3.2 V/μm driving voltage it switches in 180 μs at 30 °C. [ABSTRACT FROM AUTHOR]

The effects of anchoring phenomenon on the electric Frederiks transition threshold field in a nematic liquid crystal doped with ferroelectric nanoparticles are discussed. The polarizability of these nanoparticles in combination with confinement effects cause the drastic effects on the ferronematic systems. This study is based on Frank free energy and Rapini–Papoular surface energy for ferronematic liquid crystal having finite anchoring condition. In the case of different anchoring boundary conditions, the Euler–Lagrange equation of the total free energy is numerically solved by using the finite difference method together with the relaxation method and Maxwell construction to select the physical solutions and therefore investigate the effects of different anchoring strengths on the Frederiks transition threshold field. Maxwell construction method is employed to select three periodic solutions for nematic liquid crystal director at the interfaces of a slab. In the interval from zero to half- π , there is only one solution for the director orientation. In this way, NLC director rotates toward the normal to the surface as the applied electric field increases at the walls. Our numerical results illustrate that above Frederiks transition and in the intermediate anchoring strength, nematic molecules illustrate the different orientation at slab boundaries. We also study the effects of different anchoring strengths, nanoparticle volume fractions and polarizations on the Frederiks transition threshold field. We report that decreasing in the nanoparticle polarization results in the saturation Frederiks threshold. However, this situation does not happen for the nanoparticles volume fraction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electro-optical effects in liquid crystal helical nanostructures are analyzed. • Achievements to create liquid crystals with subwavelength helix pitch are emphasized. • Advantages of helical liquid crystals for use in photonic devices are underlined. • The unsolved problems in physics of helical smectic liquid crystals are mentioned. The origin of ferroelectricity in smectic liquid crystals is attributed to the chirality of their molecules. The chirality reduces the space symmetry and leads to the helical (helicoidal) spatial distribution of molecular axes in ferroelectric and antiferroelectric liquid crystals (FLCs and AFLCs), called a helical structure, or helical nanostructure, if its period is much less than any wavelength of visible light. Deformations of FLCs and AFLCs helical structures under the applied electric field E lead to the emergence of a number of specific electro-optical effects. This review analyzes the main results of experimental and theoretical studies of various electro-optical manifestations of FLCs and AFLCs helical nanostructures deformations, which are already used to develop displays and photonic devices of a new generation. [ABSTRACT FROM AUTHOR]

• In this work, we study a ferroelectric liquid crystal (FLC) cell as a phase-only modulator. The novelty of the approach is the use of a FLC cell with a large switching rotation angle close to 90° instead of the typical value used in display applications, which is less than 45 ∘. • We show that when the LC layer is a half-wave retarder, this device provides a binary π phase modulation for any input state of polarization and with maximum light conversion efficiency, thus being useful even for unpolarized light. This situation is not possible with the common nematic LC modulators or with standard FLC modulators of smaller rotation angles. • The main physico-chemical properties of the liquid crystalline mixture used to fabricate the FLC modulator are studied. In addition, we perform a reverse engineering procedure aimed at verifying the modulator's physical parameters and the binary π -phase modulation. In this work a ferroelectric liquid crystal (FLC) modulator with a non-standard large switching rotation angle, close to 90 ∘ , is fabricated and characterized. The modulator acts as a switchable wave-plate with an in-plane rotation of the principal axis under the action of a bipolar voltage. In the ideal situation of half-wave retardance, the device is shown to behave as a binary π phase modulator independently of the input state of polarization. We provide physico-chemical properties of the liquid crystalline mixture used to fabricate the FLC modulator with such large switching angle. The characterization method of the device optical properties is presented, which allows the localization of the two LC stable states, the unambiguous determination of the rotation angle, and the evaluation of the spectral retardance function. We demonstrate the polarization-independent π phase shift using an adapted Young's type interferometer for real-time measurements, where we further analyze the operational frequency limits of the device. This FLC operational mode can be exploited to produce binary-phase polarization-independent diffractive optical elements. [ABSTRACT FROM AUTHOR]