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The research and development of push‐pull tetraene chromophores (PPT‐phores) have contributed greatly to the field of organic electro‐optic (EO) materials and devices since the inauguration of CLD‐1 in 2001. This study is thus a systematic contribution to synthesize and characterize a series of centro‐arylated PPT‐phores based on strong electron‐donating tetrahydroquinolinyl groups and variable strong electron‐accepting tricyanofuran derivatives. In particular, we report the crystallographic data to show various packing modes of these PPT‐phores with detailed information about bond length alternation and intermolecular interactions, the optical absorption edges of guest‐host polymers by the Tauc model, and the anisotropy and dispersion of Pockels tensors for the poled polymers by attenuated total reflection spectroscopy. Such analyses have not been addressed to any significant extent previously and are fundamentally important to the future development of PPT‐phore‐based EO materials and devices. The poled films of several centro‐arylated PPT‐phores in polycarbonates exhibited large EO activities, excellent thermal stability, and tunable optical transparency at the telecom O‐ and C‐band. The study demonstrates the effectiveness of π‐bridge centro‐arylation enabled by molecular shape modification and rigidity enhancement, over the relatively flexible and labile thioether or alkoxy groups, in rational design of hyperpolarizable PPT‐phores for high‐performance EO polymers. [ABSTRACT FROM AUTHOR]

Multifluorinated aromatics serve as supramolecular synthons in the research of organic electro‐optic (EO) materials by exploiting π‐π stacking interaction between the aromatic hydrocarbon and multifluorinated aromatic groups for performance improvement. However, non‐classical hydrogen bonding remains largely unexplored in fluorinated EO dendrimers. In this study, three Fréchet‐type generation 1 benzyl ether co‐dendrons were synthesized by replacing one benzyl group with 2,3,5,6‐tetrafluorobenzyl (p‐HF4Bz), pentafluorobenzyl (C6F5Bz), and 2,3,4,5‐tetrafluorobenzyl (o‐HF4Bz) groups, to afford the benzoic acid derivatives D1, D2, and D3, which were further bonded to the donor and π‐bridge moieties to afford three co‐dendronized push‐pull phenyltetraene chromophores EOD1, EOD2, and EOD3, respectively. The weak C−H⋅⋅⋅X (X=O, F) interactions in the crystal structure of D1 cumulatively add to the benzoic acid dimers to form an extended hydrogen‐bonded network, while D2 is crystallized into a centric one‐dimensional chain with strong intermolecular interactions. The poled films of EOD1 with PMMA exhibited the largest and most stable EO activity with optical homogeneity among the series. The results identify the effectiveness of weak but favorable hydrogen bonds enabled by the enhanced carbon acidity of p‐HF4Bz synthon in D1, over the interactions in D2 and D3, for the rational design of supramolecular EO dendrimers. [ABSTRACT FROM AUTHOR]

In the present paper, the reflection and transmission properties of a one-dimensional photonic crystal made of alternate layers of isotropic dielectric medium and electro-optic nanocomposite structurally chiral medium (NSCM) are investigated. The electro-optic NSCM is a nanocomposite medium consisting structurally chiral material (SCM) where the silver nanoparticles are randomly dispersed inside it. The numerical results show three kinds of photonic bandgap in this structure, including traditional Bragg gap, circular Bragg gap and plasmonic absorption bandgap, which is due to the plasmonic resonance and absorption of the silver nanoparticles. The effect of the external low-frequency electric field is investigated on the reflection and transmission spectra of the structure. It is shown that the impact of the applied voltage depends on the value of the tilt angle and the maximum changes are experienced for the case of χ = 90 ∘ . Also, the results show that the width of the traditional and circular Bragg gaps is sensitive to the applied voltage; however, the variation of the circular Bragg gap is more noticeable. [ABSTRACT FROM AUTHOR]

Based on an analysis of the main modern trends in the design of hyperspectral equipment, it is shown that when creating new small-sized devices for using in ground-based observation systems, the use of integrated optoelectronic circuits and optical components in planar design is promising. In particular, the expediency of using micromirror arrays in scanning systems and Mach–Zehnder planar interferometers in spectrum separation systems was noted. This makes it possible to abandon bulky, slow, and not always reliable mechanical components and create devices with on-line hyperspectral image recording. [ABSTRACT FROM AUTHOR]

The results of the research in the field of the electro-optics of nematic and smectic (ferroelectric) liquid crystals, performed at the Lebedev Physical Institute of the Russian Academy of Sciences (FIAN), as well as their applications in modulation of the amplitude, phase, or scattering of laser radiation in electrically and optically controlled transparencies (spatial light modulators); holographic memory devices; wave-field formers and image converters (including three-dimensional ones); and recognition, sensor, and other laser technique devices, are presented. [ABSTRACT FROM AUTHOR]

Abstract We present an electro‐optic modulator exploiting a metamaterial made of an array of vanadium dioxide nanorods operating in epsilon‐near‐zero regime as the active switching material in a silicon waveguide. The modulator takes advantage of the insulator‐to‐metal transition of vanadium dioxide along with near‐zero effective permittivity to achieve a modulation depth of 19.7 dB µm–1 in a footprint of 1.6 µm × 1 µm over a broad range of wavelengths. Using simulations, we demonstrate how the effective permittivity of the metamaterial can be tuned to a near‐zero value by varying the nanorod geometry to increase the modulation depth. The paper further investigates a novel hexagonal array design using the metamaterial nanorods to obtain a lower insertion loss and high modulation depth. The results provide insight into the design of ultra‐compact epsilon‐near‐zero modulators with high operation frequencies and low insertion losses.

In this work, we present an Opto-Electro-Mechanical Modulator (OEMM) for RF-to-optical transduction realized via an ultra-coherent nanomembrane resonator capacitively coupled to an rf injection circuit made of a microfabricated read-out able to improve the electro-optomechanical interaction. This device configuration can be embedded in a Fabry–Perot cavity for electromagnetic cooling of the LC circuit in a dilution refrigerator exploiting the opto-electro-mechanical interaction. To this aim, an optically measured steady-state frequency shift of 380 Hz was seen with a polarization voltage of 30 V and a Q-factor of the assembled device above 10 6 at room temperature. The rf-sputtered titanium nitride layer can be made superconductive to develop efficient quantum transducers. [ABSTRACT FROM AUTHOR]

In the current work, a theoretical computer study by using visual basic.net was conducted to study the possibility of the tuning method in obtaining magnetic lenses without rotation and distortion. A new objective function was developed to show the magnetic flux density distribution of single-gap magnetic lenses. The variables effect of optimization imposed by the objective function, on the study, properties and redesigning electrodes produced by the imaging fields, was studied. The study covered all of the areas of single-gap magnetic imaging. In the study of the objective function used, it is based on two variables of the engineering optimization, namely the thickness of the gap S and the diameter of the aperture D. As for the optimization variable of the imaging field irritation NI, it is neglected because it does not affect the optical properties where S and D are of great importance in magnetic lens design as it was possible to obtain spin less and distortion-free images by choosing the appropriate values ​​of the ratios between the gap and the aperture of the lens. [ABSTRACT FROM AUTHOR]

We present an electro‐optic modulator exploiting a metamaterial made of an array of vanadium dioxide nanorods operating in epsilon‐near‐zero regime as the active switching material in a silicon waveguide. The modulator takes advantage of the insulator‐to‐metal transition of vanadium dioxide along with near‐zero effective permittivity to achieve a modulation depth of 19.7 dB µm–1 in a footprint of 1.6 µm × 1 µm over a broad range of wavelengths. Using simulations, we demonstrate how the effective permittivity of the metamaterial can be tuned to a near‐zero value by varying the nanorod geometry to increase the modulation depth. The paper further investigates a novel hexagonal array design using the metamaterial nanorods to obtain a lower insertion loss and high modulation depth. The results provide insight into the design of ultra‐compact epsilon‐near‐zero modulators with high operation frequencies and low insertion losses. [ABSTRACT FROM AUTHOR]

Nature is highly efficient at producing chiral compounds that are enantiomerically pure. The inherent chirality of naturally occurring biomolecules means that many have the potential to be used as chiral dopants for cholesteric liquid crystal (CLC) systems. Though many biomolecules have been identified as chiral dopants, many remain yet to be probed for their ability to function as chiral dopants. Here, 10 naturally occurring biomolecules comprised of steroids and bile acids were tested as chiral dopants for CLCs. Progesterone was identified as having high miscibility with nematic liquid crystals and was used in responsive liquid crystal devices. Progesterone-doped CLC devices were fabricated to exhibit either normal mode or reverse mode switchable behavior. Polymer stabilized CLCs (PSCLC) devices exhibiting dynamic electro-optic red- and blue-tuning behaviors were also fabricated. Furthermore, immiscible lithocholic acid was synthetically modified to afford two derivatives that were miscible at 10 wt. % in nematic liquid crystals. The two lithocholic acid derivatives were used as chiral dopants and incorporated into polymer stabilized CLCs which exhibited blue tuning behavior. [ABSTRACT FROM AUTHOR]

Modern applications of polymer-dispersed liquid crystals (PDLC) made of liquid crystal droplets dispersed in polymer matrices continue to grow in popularity. They include privacy and smart windows, flexible diffusers, advanced displays, energy storage, and energy harvesting devices, to name a few. An electrically controlled switching between opaque and transparent states of PDLC films enables their numerous applications. An applied electric field reorients an average director of a liquid crystal droplet resulting in a gradual transition from an opaque to a transparent state. A fully transparent state is observed if the refractive index matching is achieved. As a rule, electro-optical characterization of polymer dispersed liquid crystals is performed using a laser. As a result, basic physical parameters such as switching times, contrast ratio, and transmittance are obtained for a single wavelength of light. Even though the spectral dependence of electro-optical properties of PDLC films was mentioned in several papers, systematic studies reporting the dependence of contrast ratio, transmittance, and switching curves of PDLC films on the wavelength of light are still missing. In this paper, electrically controlled spectral properties of PDLC films are reported. The obtained dependence of the contrast ratio and transmittance on the wavelength of light can be used for the optimization of electro-optical performance of polymer-dispersed liquid crystals. [ABSTRACT FROM AUTHOR]

In organic π‐conjugated crystals, enhancing molecular optical nonlinearity of chromophores (e.g., first hyperpolarizability β ≥ 300 × 10−30 esu) in most cases unfortunately results in zero macroscopic optical nonlinearity, which is a bottleneck in organic nonlinear optics. In this study, a new class of nonlinear optical organic crystals introducing a chromophore possessing an extremely large first hyperpolarizability is reported. With newly designed 4‐(4‐(4‐(hydroxymethyl)piperidin‐1‐yl)styryl)‐1‐(pyrimidin‐2‐yl)pyridin‐1‐ium (PMPR) chromophore, incorporating a head‐to‐tail cation‐anion OH⋯O hydrogen‐bonding synthon and an optimal selection of molecular anion into crystals results in extremely large macroscopic optical nonlinearity with effective first hyperpolarizability βiiieff$\beta _{{\rm{iii}}}^{{\rm{eff}}}$ of 335 × 10−30 esu. This is in sharp contrast to zero βiiieff$\beta _{{\rm{iii}}}^{{\rm{eff}}}$ value for previously reported analogous crystals. An ultrathin PMPR crystal with a thickness of ≈10 µm exhibits excellent terahertz (THz) wave generation performance. Both i) broadband THz wave generation with a wide flat‐spectral‐band in the range of 0.7–3.4 THz defined at −3 dB and high upper cut‐off generation frequency of > 7 THz as well as ii) high‐generation efficiency (5 times higher THz amplitude than ZnTe crystal with a mm‐scale thickness) are simultaneously achieved. Therefore, new PMPR crystals are highly promising materials for diverse applications in nonlinear optics and THz photonics. [ABSTRACT FROM AUTHOR]

This work reports a series of new organic electro‐optic salt crystals possessing unusual orthogonal dipole‐coupling assembly that act as dimple‐free THz generators. In the new crystals, optically anisotropic aromatic anions introducing highly electronegative fluorinated substituents are orthogonally assembled with optically anisotropic nonlinear optical benzothiazolium cations. These orthogonal cation–anion assembled crystals exhibit strong suppression of intrinsic THz phonon modes along the polar axis, which results in a wide THz absorption‐free range from 1.5 to 4.0 THz without substantial absorption peaks. This is sharply in contrast to previous benchmark crystals with parallel cation–anion assembly; for example, in analogous crystals, several strong absorption peaks appear in this frequency range. This absence of strong absorption peaks is attributed to the orthogonal cation–anion dipole coupling assembly, the formation of fluorinate‐induced strong interionic interactions, and a high packing ability of uniaxial anions. With top‐level macroscopic optical nonlinearity, new orthogonal‐dipole assembled crystals make dimple‐free THz wave generation possible in the range of about 1.5–4.0 THz, which is very beneficial for characterizing signature peaks related to molecular phonon motions of analytes in THz spectroscopy. Therefore, orthogonal molecular assembly of optically highly anisotropic molecules provides an efficient way to substantially reduce and control intrinsic THz phonon modes. [ABSTRACT FROM AUTHOR]

We investigated the influence of chalcopyrite (CuFeS 2) nanoplatelets on the ordering of uniform and twist-bend nematic phases of achiral bend-shaped dimers, employing polarized optical microscopy, optical and electro-optical measurements. Specifically, aliphatic amine surface-functionalized hydrophobic chalcopyrite nanoplatelets were synthesized and characterized by XRD, TEM, and IR-vis-UV spectroscopy. Nanocomposites of the liquid crystal compound 1",9"-bis(4-cyanobiphenyl-4'-yl)nonane (CB9CB) with the nanoplatelets were prepared. The study encompasses an assessment of the thermodynamic stability of the nanocomposites, constructing the corresponding phase diagram as a function of temperature and nanoplatelet mass fraction. Large phase temperature shifts were observed for minute mass fractions of NPs. Birefringence measurements were performed to investigate the orientational order parameter and the conical tilt angle's dependence on the mass fraction of the nanoplatelets and the temperature. Additionally, we measured a Fréedericksz-like reorientation transition voltage threshold and switching times as functions of the mass fraction and temperature. A huge increase of the voltage threshold was measured in the twist-bend nematic phase. The dependence of the viscoelastic coefficient ζ on NPls' mass fraction was investigated. The splay elastic constant of the helicoidal structure was estimated, using a coarse grain approximation, to be two orders of magnitude higher than in the uniform nematic phase. Finally, in the twist-bend nematic phase, the impact of temperature and nanoplatelets mass fraction on the hysteresis loop of the reorientation transition was investigated. • Phase diagram of CuFeS2-nanoplatelets dispersed in CB9CB liquid crystal. • Huge increase of the reorientation transition threshold voltage in the twist bend phase. • Estimation of the splay elastic constant of the helicoidal structure. • Large phase temperature shifts for minute mass concentration. [ABSTRACT FROM AUTHOR]

Broad temperature range ferrielectric liquid crystal mixture FerriLCM-1 was previously developed in 2022 (Pozhidaev et al. 2022). In that work dielectric and electro-optical properties of the mixture were studied at room temperature. Electrically induced birefringence index reached 0.01 at a wavelength of 532 nm with response times of 300 μ s. In this paper we continue the FerriLCM-1 properties investigation in a wide temperature range from the room ones till the isotropic phase transition temperature. It is found that one of the critical electric fields is almost temperature independent, while the Kerr coefficient of quadratic electro-optical effect in deformed helix ferroelectric (DHF) mode grows with temperature increase. This leads to an increase in the depth of phase modulation. Another critical electric field decreases smoothly with temperature rising. At 47–50 °C two critical electric fields merge, while temperature dependencies of all other dielectric and electro-optical parameters of the mixture are continuous and smooth functions. At about 50 °C the maximum electrically induced birefringence in DHF-mode is Δ n eff E = 0. 022 under the applied electric field E = 0. 4 V/ μ m and with 80 μ s response time. FerriLCM-1 mixture operating in the DHF-mode exhibits a giant Kerr coefficient of 1700 nm/V 2 (or even up to 2900 nm/V 2 at λ = 400 nm) at the temperature of 85 °C combined with a 50 μ s response time. This is the highest value of K kerr coefficient among liquid crystals. All these properties make ferrielectric liquid crystal mixture FerriLCM-1 suitable for solving various problems of phase modulation of light and use in low-voltage devices. [Display omitted] • A ferrielectric liquid crystal mixture was investigated over a temperature range from room temperatures up to 100 °C. • The mixture provides a giant Kerr coefficient up to 2900 nm/V2 at λ = 400 nm and temperature of 85 °C. • An electrically controlled phase shift by 2 π in 80 μ s was achieved at control voltage of 12 V and temperature of 50 °C. [ABSTRACT FROM AUTHOR]

Liquid crystal (LC) droplets have fascinating properties, such as anisotropic properties, in response to external stimuli. As LC droplet size may determine the proper application of soft composites, various results from numerical simulations and experimental observations of LC droplets are reported. Here, detailed topological responses of individual bipolar droplets to electric fields, are shown. The integration of each response influences the entire electro‐optic behavior. Monodispersed LC bipolar droplets are fabricated in a polyvinyl alcohol‐dissolved aqueous solution via a membrane‐emulsification method. The planar anchoring, provided by the polyvinyl alcohol surface, and surface elasticity, guide the entire LC director configuration, associated with topological defects, in the droplets. By simply blade‐coating the solution, bipolar axes of the droplets can be randomly placed on a flat substrate. Two different subsequential stages are found when applying voltages: 1) director reorientation, which is threshold‐less and 2) topological defect movement, which exhibits a threshold‐like behavior. Various initial directions of the bipolar axes with respect to the field direction provide the transition voltage between these two stages. It is believed that this study can provide important clues to handle several fundamental issues in electro‐optics of encapsulated LCs, such as the determination of response times, threshold, and operating voltages. [ABSTRACT FROM AUTHOR]

Cavity-enhanced emission of electrically controlled semiconductor quantum dots (QDs) is essential in the development of bright quantum devices for real-world quantum photonic applications. Combining the circular Bragg grating (CBG) approach with a PIN-diode structure, we propose and implement designs for ridge-based electrically contacted QD-CBG resonators. Through fine-tuning of device parameters in numerical simulations and deterministic nanoprocessing, we produced electrically controlled single QD-CBG resonators with excellent electro-optical emission properties. These include multiple wavelength-tunable emission lines and a photon extraction efficiency (PEE) of up to 30.4(3.4)%, where refined numerical optimization based on experimental findings suggests a substantial improvement, promising PEE > 50%. Additionally, the developed quantum light sources yield single-photon purity reaching 99.2(2)% and photon indistinguishability of 75(5)% under quasi-resonant p-shell excitation. Our results present high-performance quantum devices with combined cavity enhancement and deterministic charge-environment controls, which are relevant for the development of photonic quantum information systems such as complex quantum repeater networks.

In this work, we present an Opto-Electro-Mechanical Modulator (OEMM) for RF-to-optical transduction realized via an ultra-coherent nanomembrane resonator capacitively coupled to an rf injection circuit made of a microfabricated read-out able to improve the electro-optomechanical interaction. This device configuration can be embedded in a Fabry–Perot cavity for electromagnetic cooling of the LC circuit in a dilution refrigerator exploiting the opto-electro-mechanical interaction. To this aim, an optically measured steady-state frequency shift of 380 Hz was seen with a polarization voltage of 30 V and a Q-factor of the assembled device above 106 at room temperature. The rf-sputtered titanium nitride layer can be made superconductive to develop efficient quantum transducers.

Fine tuning and switching of nonlinear optical response of ferrocene chromophores has been an area of considerable significance as evidenced by a large number of reports in the current literature. In this personal account, we present linear/nonlinear behavior and structure‐activity relationships of several classes of donor‐π‐acceptor designs using organometallic and organic materials, developed by our research group during the last decade. The results especially the electronic absorption spectral and the hyper‐Rayleigh scattering have been supported by theoretical calculations. Exploiting the redox behavior of ferrocene donor, we have demonstrated switching of quadratic nonlinear optical responses with reversible redox chemistry, which is a useful attribute of nonlinear optical materials. Based on the ease in synthesis, structure diversification and structure‐based large and switchable second‐order optical nonlinearity, these materials are potential candidates for electro‐optic applications. [ABSTRACT FROM AUTHOR]

Nonlinear optical (NLO) single crystals with high quality are the pillars for the development of new devices that fulfil the demands of society. Nowadays, NLO single crystals are very attractive for the photonic applications particularly for terahertz (THz) photonics. The reason for their popularity is that these crystals can produce very powerful and ultra wideband THz waves due to their high nonlinear susceptibility. In this review paper, we deal with the challenges and progresses in the evolution of NLO single crystals for THz wave generation and detection. Here, we review the single crystal growth that how and by which method single crystal is grown. We summarize the structures, intermolecular and intramolecular interactions, their properties and how they generate and detect the THz waves. Widely used single crystals at present are DAST, BNA, OH1, amino acid-based single crystals, etc. [ABSTRACT FROM AUTHOR]

Nature is highly efficient at producing chiral compounds that are enantiomerically pure. The inherent chirality of naturally occurring biomolecules means that many have the potential to be used as chiral dopants for cholesteric liquid crystal (CLC) systems. Though many biomolecules have been identified as chiral dopants, many remain yet to be probed for their ability to function as chiral dopants. Here, 10 naturally occurring biomolecules comprised of steroids and bile acids were tested as chiral dopants for CLCs. Progesterone was identified as having high miscibility with nematic liquid crystals and was used in responsive liquid crystal devices. Progesterone-doped CLC devices were fabricated to exhibit either normal mode or reverse mode switchable behavior. Polymer stabilized CLCs (PSCLC) devices exhibiting dynamic electro-optic red- and blue-tuning behaviors were also fabricated. Furthermore, immiscible lithocholic acid was synthetically modified to afford two derivatives that were miscible at 10 wt. % in nematic liquid crystals. The two lithocholic acid derivatives were used as chiral dopants and incorporated into polymer stabilized CLCs which exhibited blue tuning behavior.

A relatively simple fiber sensor system for high-power electromagnetic field measurements is presented. The system utilizes an all-dielectric fiber tip sensor head with CdTe electro optic (EO) crystal as an electric field transducer. The fiber sensor of small size converts electric field strength into modulation of light power. The rise time of the EO sensor is measured and evaluated theoretically. The system can be used for ultra-wideband high-power electric field measurements. [ABSTRACT FROM AUTHOR]

Electro‐optic (EO) modulation allows the conversion of electrical signals to optical pulses and is widely employed in telecommunications and chip‐to‐chip interconnects. Recently, hybrid organic–inorganic perovskites (HOIPs) have been explored as candidates for EO modulators. To improve the EO performance, it is envisioned that halide doping will lower the symmetry of the crystal, enhancing spontaneous polarization. However, mixed halide perovskites are often associated with ion migration, which may impact their EO properties. Thus, the influence of ion migration on the EO efficiency is investigated using Br‐doped Dion–Jacobson quasi‐2D HOIPs, (4AMP)(MA)Pb2(Brx/I1−x)7 (4AMP = 4‐(aminomethyl)piperidinium, MA = methylammonium). While density functional theory predicts a greater spontaneous polarization for the Br‐doped sample, it is found that experimental results are affected by ion migration. The EO coefficient of the Br/I mixed sample is 95 pm V−1 at 1 kHz (≈50× higher than the undoped sample), but the response falls off rapidly with frequency. This frequency dependence is correlated with impedance spectroscopy, showing that the large EO signal results from ion migration. This study shows that ion migration impacts the EO analysis of mixed halide perovskites and must be considered in future EO studies. [ABSTRACT FROM AUTHOR]

Organic π‐conjugated crystals with second‐order optical nonlinearity are considerably attractive materials for diverse terahertz (THz) wave photonics. An overview of the research of organic nonlinear optical (NLO) crystals for THz wave generation, detection, and applications is provided here. First, the status of organic NLO crystals compared to other alternative THz materials is described. Second, the basic theory and requirements for organic THz generators and detectors are explained. Third, with a primary focus on the organic NLO crystals that have been developed during the last decade, various molecular engineering approaches are discussed from the perspective of THz photonics. Finally, various types of high‐power broadband coherent THz sources and their applications in THz nonlinear optics are discussed. [ABSTRACT FROM AUTHOR]

Introduction/purpose: The Modulation Transfer Function (MTF) is a useful tool for an imaging system performance analysis. It is used in Electro-Optical (EO) system design, verification of targeted system parameters, but also in optimization tasks for systems under test. This methodology based on the linear systems theory allows the performance analysis of complicated EO systems to be divided into subsystems. In this paper, the MTF methodology will be presented and explained, followed by the measurements performed in the electro-optical laboratory. The MTF measurements were performed on three types of cameras in different spectral bands, after which the results were compared to the model expectations and theoretical limits for the imaging system. For one of the sensors, the limiting frequency was also measured using the USAF 1951 test target which allowed the comparison between the methods. Methods: Laboratory measurements and theoretical mathematical calculations. Results: Based on the laboratory and theoretical results, the measurement results were further analyzed. Conclusion: The measurements have proven that the calculated cutoff frequency and the MTF curve represent the limit for the real measured system performance. Therefore, this study has confirmed that the MTF can be convenient for finding system limitations and bottlenecks and for increasing the overall performance of the system. / Введение/цель: Функция модуляции передачи (MTF) является полезным инструментом для анализа эффективности системы формирования изображений. Она используется при разработке электрооптических систем (EO), проверке целевых параметров системы, а также в задачах оптимизации тестируемой системы. Данная методология основана на теории линейных систем и обеспечивает возможность разделения анализа эффективности сложных систем ЭО на подсистемы. В настоящей статье представлена и объяснена методология MTF, а также приведены примеры измерений, произведенных в электрооптической лаборатории. Измерения MTF проводились с помощью трех видов камер в разных спектральных диапазонах, после чего результаты сравнивались с прогнозируемыми моделями и теоретическими пределами системы формирования изображения. Методы: Лабораторные измерения и теоретическая математическая статистика. Результаты: Результаты измерений были дополнительно проанализированы на основании проведенных лабораторных и теоретических результатов. Выводы: Проведенные измерения показали, что рассчитанная предельная частота и кривая MTF представляют собой границу реальных измеренных характеристик эффективности системы. Таким образом, исследование подтвердило, что MTF может способствовать выявлению системных ограничений и узких мест, а также повышению общей эффективности системы. Разработаны рекомендации по дальнейшей оптимизации систем формирования изображений. / Uvod/cilj: Modulaciona funkcija prenosa (MTF) koristan je alat za analizu performansi sistema za obradu slike. Koristi se u dizajniranju elektrooptičkih (EO) sistema, pri proveri ciljanih parametara sistema, ali i u zadacima optimizacije testiranih sistema. Ova metodologija, zasnovana na teoriji linearnih sistema, omogućava da se analiza performansi složenih EO sistema podeli na podsisteme. MTF metodologija najpre je predstavljena i objašnjena, a zatim je prikazano merenje izvršeno u elektrooptičkoj laboratoriji. MTF merenja izvedena su na tri tipa kamera, u različitim spektralnim opsezima, nakon čega su rezultati upoređeni sa očekivanim modelima i teorijskim ograničenjima sistema za obradu slike. Metode: Laboratorijska merenja i teorijska matematička izračunavanja. Rezultati: Na osnovu laboratorijskih i teorijskih rezultata dodatno su analizirani rezultati merenja. Zaključak: Merenja su dokazala da izračunata granična frekvencija i krivulja MTF predstavljaju granicu za stvarne performanse sistema. Potvrđeno je da MTF može biti pogodan za pronalaženje ograničenja i uskih grla sistema, kao i za poboljšanje ukupnih performansi sistema.

Modern applications of polymer-dispersed liquid crystals (PDLC) made of liquid crystal droplets dispersed in polymer matrices continue to grow in popularity. They include privacy and smart windows, flexible diffusers, advanced displays, energy storage, and energy harvesting devices, to name a few. An electrically controlled switching between opaque and transparent states of PDLC films enables their numerous applications. An applied electric field reorients an average director of a liquid crystal droplet resulting in a gradual transition from an opaque to a transparent state. A fully transparent state is observed if the refractive index matching is achieved. As a rule, electro-optical characterization of polymer dispersed liquid crystals is performed using a laser. As a result, basic physical parameters such as switching times, contrast ratio, and transmittance are obtained for a single wavelength of light. Even though the spectral dependence of electro-optical properties of PDLC films was mentioned in several papers, systematic studies reporting the dependence of contrast ratio, transmittance, and switching curves of PDLC films on the wavelength of light are still missing. In this paper, electrically controlled spectral properties of PDLC films are reported. The obtained dependence of the contrast ratio and transmittance on the wavelength of light can be used for the optimization of electro-optical performance of polymer-dispersed liquid crystals.

The recently discovered ferroelectric nematic (NF) liquid crystals (LCs) with over 0.04 C m−2 ferroelectric polarization and 104 relative dielectric constants, coupled with sub‐millisecond switching, offer potential applications in high‐power super capacitors and low voltage driven fast electro‐optical devices. This paper presents electrical, optical, and electro‐optical studies of a ferroelectric nematic LC material doped with commercially available chiral dopants. While the NF phase of the undoped LC is only monotropic, the chiral NF phase is enantiotropic, indicating a chirality induced stabilization of the polar nematic order. Compared to undoped NF material, a remarkable improvement of the electro‐optical switching time is demonstrated in the chiral doped materials. The color of the chiral mixtures that exhibit a selective reflection of visible light in the chiral NF phase, can be reversibly tuned by 0.02–0.1 V µm−1 in‐plane electric fields, which are much smaller than typically required in full‐color cholesteric LC displays and do not require complicated driving scheme. The fast switchable reflection color at low fields has potential applications for LC displays without backlight, smart windows, shutters, and e‐papers. [ABSTRACT FROM AUTHOR]

Featured Applications: optical communications, optical sensors. Liquid crystals are interesting linear and nonlinear optical materials used to make a wide variety of devices beyond flat panel displays. Liquid crystalline materials can be used either as core or as cladding of switchable/reconfigurable waveguides with either an electrical or an optical control or both. In this paper, materials and main device structures of liquid crystals confined in different waveguide geometries are presented using different substrate materials, such as silicon, soda lime or borosilicate glass and polydimethylsiloxane. Modelling of the behaviour of liquid crystal nanometric molecular reorientation and related refractive index distribution under both low-frequency electric and intense optical fields is reported considering optical anisotropy of liquid crystals. A few examples of integrated optic devices based on waveguides using liquid crystalline materials as core for optical switching and filtering are reviewed. Reported results indicate that low-power control signals represent a significant feature of photonic devices based on light propagation in liquid crystals, with performance, which are competitive with analogous integrated optic devices based on other materials for optical communications and optical sensing systems. [ABSTRACT FROM AUTHOR]

Ultra‐broadband THz photonics covering the 0.3–20 THz range provides a very attractive foundation for a wide range of basic research and industrial applications. However, the lack of ultra‐broadband THz devices has yet to be overcome. In this work, high‐density organic electro‐optic crystals are newly developed for efficient THz wave generation in a very broad THz spectral range and are successfully used for a broadband THz time‐domain spectroscopy. The new organic THz generator crystals, namely the OHP‐TFS crystals, have very low void volume, high density, and are shown to cover the ultra‐broadband THz spectrum up to about 15 THz, which cannot be easily accessed with the more widely used inorganic‐based THz generators. In addition to the very favorable broadband properties, the generated THz electric‐field amplitude at the pump wavelength of 1560 nm is about 40 times higher than that generated by a commercial inorganic THz generator (ZnTe crystal). By using the newly developed OHP‐TFS as generation crystal in a compact table‐top all‐organic THz time‐domain spectrometer based on a low‐cost telecom fiber laser, the optical characteristics of a model material are successfully determined in the broad 1.5–12.5 THz range with high accuracy. [ABSTRACT FROM AUTHOR]