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In this study, semitransparent lead films serve as substrates for depositing niobium pentoxide thin films, forming versatile electro‐optical devices. Using vacuum evaporation and ion sputtering techniques at ≈10−5 mbar, stacked layers of crystalline Pb and amorphous Nb2O5 are created. This process reduces free carrier absorption in Nb2O5 and forms Urbach tail states with a width of 0.91 eV. Pb/Nb2O5 thin films exhibit remarkable broadband absorption, exceeding 440% in the visible and 98% in the infrared. Moreover, Pb substrates induce a redshift in Nb2O5’s energy bandgap. Electrical analysis using impedance spectroscopy on Pb/Nb2O5/Ag structures reveals their series/parallel resonance and bandstop filter properties. Notably, the bandstop filters exhibit reflection coefficient minima at a notch frequency of 1.66 GHz, with a bandwidth of 280 MHz, return loss of 26 dB, and voltage standing wave ratio of 1.13. These findings underscore the device's potential for wide‐ranging electro‐optical applications across the electromagnetic spectrum. [ABSTRACT FROM AUTHOR]

Airborne electro-optical/infrared reconnaissance systems could scan a large area by using an array detector and stitching the image sequence to produce a large area coverage image. During the scanning and imaging process, the reconnaissance system may experience various disturbances that can result in the failure of stitching ground area images. To investigate the suppression method of disturbance and achieve seamless area coverage, we first introduce the standard coordinate systems and conversion relationships used in Geo-scanning imaging. We describe the basic implementation of Geo-scanning ground imaging coverage and highlight the problems encountered in achieving seamless ground area coverage. To ensure seamless ground coverage, Geo-scanning uses compensating angular rate commands for cross-roll and pitch scanning gimbal. The process of Geo-scanning is then simulated in the simulation platform and the effectiveness of the designed perturbation suppression method is verified. The feasibility of suppressing multiple perturbations simultaneously is verified. A unified angular rate compensation command is proposed to suppress the effects of forward motion, heading static angular disturbance, and attitude tilt. This will avoid the need for different compensation command expressions for different perturbations and enable resistance to multiple perturbations simultaneously. The proposed method will make the angular rate command for platform scan imaging more robust and avoiding image stitching cracks, ensuring smooth image stitching from a motion control perspective and achieve seamless area coverage. [ABSTRACT FROM AUTHOR]

Current methods of performing Initial Orbit Determination (IOD) in near-earth orbital regions cannot be directly extended to cislunar space due to changes in gravitational models that must be utilized. For the case of cislunar orbits, the Moon’s gravitational influence necessitates that orbital motions be described by three-body dynamics. Three-body dynamics produce orbits that are generally not elliptical, fixed to an orbital plane, or geometrically simple. This change in assumptions that can be made complicates the task of performing IOD and has led to the investigation of alternative methods and features to classify cislunar orbit parameters. In this paper, we explore the potential of utilizing Machine Learning (ML) algorithms to constrain potential IOD search spaces to specific cislunar families. We accomplish this by training the ML classifier to predict cislunar family from a light curve. To generate training data for this ML effort, we introduce a novel simulation pipeline that produces radiometrically validated light curves using the Digital Imaging and Remote Sensing Image Generation (DIRSIG™) engine. This pipeline ingests various parameters, including: initial Circular Restricted Three-Body Problem (CR3BP) state vectors, satellite material properties, telescope optical properties, and satellite 3D models. The pipeline produces light curves capturing the influence of these factors on the observed visual magnitude signature as a function of elapsed time and phase angle. This pipeline was utilized to produce approximately 3500 light curves of various cislunar orbital families as captured from the perspective of two observing locations: the spaced-based Earth-Moon L1 point, and a Lunar surface based point. These light curves were used as training datasets for neural network models to perform classification of cislunar family via input time-series vectors consisting of two features: visual magnitude and phase angle. Our machine learning technique first uses a warping technique to construct constant sized observational input of the light curves into a multi-layer perceptron, the architecture of which was chosen by a search over a large landscape of possibilities optimizing for validation prediction accuracy. The selected model was then trained on various scenarios of input data, again doing a search over several available hyper-parameters. It was found that the trained models were able to achieve test data-set accuracy of 93.4% for light curves captured from the face of the moon, and 87.5% when combined with light curves captured from the space-based L1 point. [ABSTRACT FROM AUTHOR]

In this work, the impact of Ag–In–S quantum dots (QDs) on the dielectric and electro-optical characteristics of E7 nematic liquid crystal (NLC) is investigated. To realize the objective, various concentrations of Ag–In–S QDs (0.2, 0.4, 0.6, 0.8, and 1 wt%) were added to E7 NLC, and the resulting composites were then introduced into homogeneous, homeotropic, and twisted nematic aligned cells. The temperature dependence property of the parallel and perpendicular components of the dielectric constant (ɛ∥ & ε ⊥ ) for pure and QDs-doped NLCs was measured. ɛ∥ significantly enhanced in the presence of 0.8 wt% of the QDs, which led to a ~ 23% rise in the dielectric anisotropy of the system. The dielectric results demonstrated that NLC hosts prompt QDs to form self-assembled arrays within the NLC system. In addition, electro-optical measurements revealed the considerable impact of QDs doping on the reduction of threshold voltage (Vth). Importantly, a ~ 15% decrease in Vth was observed for NLC doped with 0.8 wt% of the QDs compared to pure NLC. Besides, the addition of QDs significantly accelerates the NLC electro-optical response. The switch-on and -off response times for the QDs-doped NLC cell were reduced by ~ 34% and ~ 41%, respectively, compared to those for the pure NLC cell. A combination of increased dielectric anisotropy, improved mutual interactions of components, and reduced rotational viscosity of the mixture may result in much faster electro-optical switching responses. The presented achievements in this study will be beneficial in the development of LC-based display panels as well as switchable smart windows. [ABSTRACT FROM AUTHOR]

In this study, high-speed mid-infrared Mach–Zehnder electro-optical modulators in x-cut lithium niobate (LN) thin film on sapphire were designed, simulated, and analyzed. The main optical parameters of three types of Mach–Zehnder modulators (MZMs) (residual LN with thickness of 0, 0.5, and 1 μm) were simulated and calculated, namely, the single-mode conditions, bending loss, separation distance between electrode edge and lithium niobate waveguide edge, optical field distribution, and half-wave voltage–length product. The main radio frequency (RF) parameters of these three types of MZMs, such as characteristic impedance, attenuation constant, RF effective index, and the –3 dB modulation bandwidth were calculated depending on the dimensions of the coplanar waveguide traveling-wave electrodes. The modulations with residual LN thickness of 0, 0.5, and 1 μm were calculated with bandwidths exceeding 140, 150, and 240 GHz, respectively, and the half-wave voltage–length product achieved was 22.4, 21.6, and 15.1 V cm, respectively. By optimizing RF and optical parameters, guidelines for device design are presented, and the achievable modulation bandwidth is significantly increased.

High-tilt angle ferroelectric liquid crystal material in surface stabilised geometry (SSFLC) is investigated for the smectic layer reorientation and its molecular dynamics by electro-optical and dielectric spectroscopy techniques. Smectic layer reorientation (5 $^o$ o to 45 $^o$ o ) is obtained by controlled cooling rate and applying electric field in the vicinity of transition temperature from chiral nematic (${N^*}$ N ∗ ) to chiral smectic C ($Sm{C^*}$ Sm C ∗ ) phase. After slow cooling down to room temperature, the stripe domain textures along the rubbing are observed with quasi-bistable states. Dielectric spectroscopy has revealed the unusual increment in the dielectric permittivity. A dielectric relaxation process at lower frequency than Goldstone mode with the increase in DC bias up to 2 $V$ V is observed in the sample cooled without any bias. This increment is found to be originated by the heliconical structure within the stripes which is seen in the optical textures recorded at the time of dielectric scan. However, this increment is not observed in the sample cooled under DC bias. Thus, there exist different phenomena in the high tilt angle SSFLC sample cooled in different conditions of DC bias; stripe domains, smectic layers reorientation, heliconical stricture and twisted structure within stripes which are significant to explore deeply in high-tilt angle ferroelectric liquid crystals. [ABSTRACT FROM AUTHOR]

Present studies demonstrate the dispersion effect of cadmium selenide quantum dots on ferroelectric liquid crystal mixture properties. Varying concentrations of cadmium selenide quantum dots (0.05 wt.%, 0.10 wt.% and 0.50 wt.%) have been taken to investigate its influence on the physical parameters of ferroelectric liquid crystal mixture KCFLC 10R. Phase transition, textural, electro-optical and photoluminescence studies have been performed in planar aligned cells. The presence of QDs disturbs the geometrical symmetry and molecular tilt of ferroelectric liquid crystal molecules which results in the modification of physical parameters of ferroelectric liquid crystal. It has been observed that doped samples have shown decrement in spontaneous polarisation and rotational viscosity. However, there is an improvement in the response time of the doped samples. The reduction in the spontaneous polarisation with voltage signifies that doped samples can operate at low voltage (~6 V) as compared to ferroelectric liquid crystal mixture (~12 V). Photoluminescence studies reveal that all the samples absorb UV light ~340 nm and produce visible emission at ~ 400 nm which can behave as UV light storage and high contrast display. This would be beneficial for luminescent displays as well as UV to visible light conversion applications. Dispersion of cadmium selenide quantum dots with varying concentration in ferroelectric liquid crystal mixture has been investigated. Temperature- as well as voltage-dependent electro-optical parameters and photoluminescence studies have been done and analysed. Fast response time has been observed in the doped samples as compared to FLC mixture. Doped samples can be operated at low voltage (~6 V) as compared to FLC mixture (~12 V) These prepared samples can be used for UV to visible light conversion applications. [ABSTRACT FROM AUTHOR]

Disperse dye red 1 (DR1) and carbon nanoparticles (CNPs) were doped separately to form polymer dispersed liquid crystal films, namely, DPDLC & CPDLC. Nematic liquid crystal (LC) and photopolymer NOA-65 were used to prepare these composite films using polymerisation-induced phase separation (PIPS) technique. In this research work, it is demonstrated that the minute concentration (0.05% wt./wt.) of DR1 and CNPs controls the LC droplet alignment and LC droplet size in polymer dispersed liquid crystal (PDLC) film. The effect of DR1 and CNPs on PDLC film has been investigated in terms of LC droplet size, transition temperature, voltage-transmittance characteristic, contrast ratio, response time, haze, and dielectric measurements. The obtained results reveal that the threshold voltage values of the composite film get reduced from 34.87 V (undoped) to 10.19 and 9.26 V, for 0.05% of DR1 and CNPs doping, respectively. The DR1 (0.05%) doped film shows improved contrast of the undoped film as compared to CNPs (0.05%) film, whereas CNPs (0.05%) doped film shows a faster response time of 2.81 ms as compared to DR1 (0.05%) doped film (3.14 ms). Dielectric analysis of undoped, DPDLC, and CPDLC films represents Debye type relaxation mode. [ABSTRACT FROM AUTHOR]

Herein, we design an optoelectronic device using phase-change materials (PCMs) and assess its ability to possess two functionalities: the perfect absorption of photonic metasurfaces and the high-density storage capability of electronic memories. Both functionalities are evaluated experimentally and via simulations. Such bifunctionalities are achieved according to the phase-transformation extent of the designed hybrid that comprises a phase-change stack having Si/SiO 2 /Au/Ge 2 Sb 2 Te 5 (GST)/indium tin oxide (ITO) and a conductive PtSi probe. The use of PCM layers either in a full crystalline or an amorphous phase causes perfect absorption. The resonant wavelength of the device can be dynamically changed by modulating the phase-change extent of the PCM layer. Generating a continuous crystalline region or separated crystalline bits inside the amorphous GST exhibits a larger tuneability of the phase-change extent than forming separated amorphous bits inside the crystalline GST, and allows for a wider bandwidth of 300 nm for perfect absorber applications. Forming amorphous bit array inside crystalline background yields discernible optical reading contrast when compared to forming a crystalline bit array. The amorphous bit array configuration has an areal density of ～500 Gbits/inch2, data rate of 5 Mbits/s, and energy consumption of 92 pJ/bit. These values render the configuration attractive for probe storage applications. Such a designed hybrid with the ability to process data photonically and store data electronically exhibit its promising for highly integrated metasurface and superb compact electro-optical computing device. [ABSTRACT FROM AUTHOR]

Multimodal fusion approaches that combine data from dissimilar sensors can better exploit human-like reasoning and strategies for situational awareness. The performance of a six-layer convolutional neural network (CNN) and an 18-layer ResNet architecture are compared for a variety of fusion methods using synthetic aperture radar (SAR) and electro-optical (EO) imagery to classify military targets. The dataset used is the Synthetic and Measured Paired Labeled Experiment (SAMPLE) dataset, using both original measured SAR data and synthetic EO data. We compare the classification performance of both networks using the data modalities individually, feature level fusion, decision level fusion, and using a novel fusion method based on the three RGB-input channels of a residual neural network (ResNet). In the proposed input channel fusion method, the SAR and the EO imagery are separately fed to each of the three input channels, while the third channel is fed a zero vector. It is found that the input channel fusion method using ResNet was able to consistently perform to a higher classification accuracy in every equivalent scenario. [ABSTRACT FROM AUTHOR]

This study has used ab initio technique to investigate the electro‐optical and electronic properties of N‐(4‐methoxybenzylidene)‐4‐butylaniline (MBBA), a nematic liquid crystal between 21 and 48 °C, surrounded by gas and acetonitrile medium, in the presence and absence of electric field. The optimization and analysis of various electro‐optical and electronic parameters along with absorption spectrum have been performed using ωB97xD/6‐311+G(d,p) and M062X/6‐311+G(d,p) methods. Under the electric field, electro‐optical parameters of MBBA surrounded by acetonitrile are increased, indicating its suitability for display device development application. Global reactivity descriptors reveal that electronic properties of the MBBA LC also high in acetonitrile medium as compared to that of the gas. Furthermore, using second order perturbation theory and the multicentered‐multipole expansion technique, the mutual interactions between a pair of MBBA molecules are examined, revealing the nematic behavior of MBBA molecule. [ABSTRACT FROM AUTHOR]

The Physico-chemical, electro-optical and spectroscopic properties of 2,3,6,7,10,11-hexakispentyloxytriphenylene (HPTP) discotic liquid crystal (DLC) have been investigated in gas and NaCl solution using B3LYP/6-311++G(d,p) and M06-2X/6-311++G(d,p) methods. Both the computational techniques yield enhanced values of electro-optical and global reactivity descriptor parameters of HPTP LC molecule in NaCl solution. Neither of the techniques reveal a red or blue shift in the absorption spectra of the LC molecule. The electron localised function (ELF) and frontier molecular orbitals have been examined. Both in gas and solvation medium, electronic circular dichroism (ECD) spectra evidence significant optical activity of the discotic LC molecule. The range-separated hybrid functional such as LC-BLYP/LC-TDDFT formalism has also been used for estimating electronic property and excitation energy of the triphenylene LC molecule; and results obtained by LC-BLYP, B3LYP, and M06-2X computations have been juxtaposed for an extensive comparison. Furthermore, molecular dynamics simulation elucidates that stability and interaction ability of HPTP LC molecule are improved in the ionic (NaCl) solution. These findings provide a new framework for understanding the structural characteristics, and electro-optical, electronic, and dynamical behaviour of discotic triphenylene analogue in ionic solution. [ABSTRACT FROM AUTHOR]

In this paper, we theoretically investigate the optical characteristics and Faraday rotation of the one-dimensional photonic structure (1-DPS) consisting of magneto-optical (MO) and dielectric (SiO2) materials containing a defect layer of electro-optical (EO) material using a 4 × 4 Berremann matrix method. The proposed defect layer inside 1-DPS is sandwiched of EO material by ITO layers. The anisotropic materials in the periodic structure, the magneto-optical and electro-optical layers are considered as cerium-substituted yttrium iron garnet (Ce:YIG) and lithium niobate (LiNbO3), respectively. The Ce:YIG (MO) and LiNbO3 (EO) materials have magnetic-field- and voltage-dependent responses such as dielectric indices of EO and MO materials. The optical properties are affected with external fields. The hybrid modes or Tamm plasmons polaritons (TPPs) modes appear at the interfaces in the periodic structure. Therefore, the transmission characteristics as well as Faraday rotation ( θ F ∘ ) and ellipticity ( ϕ ∘ ) angles get affected with the TPPs modes. The proposed study reports the transmittance, reflection, Faraday rotation and elliptical effect at the different voltage (V), magnetic field (B), thickness and incident angle of electromagnetic wave. The obtained results also show that TPPs modes tune with the variation of magnetic field and applied voltage. Hence, the optical properties and Faraday rotation of the considered structure exhibit tunable behavior with the variation of magnetic field, voltage and other material parameters. The investigated 1-DPS may be used in various tunable electro-optical or magneto-optical devices such as optical switch, memory device, isolators and modulators at optimum values of material parameters. [ABSTRACT FROM AUTHOR]

• Developed zinc oxide nanoparticles induced vertically aligned liquid crystals. • Study the effect of varying concentration of dichroic dye on textural, electro-optical, phase transition and band gap studies. • Significantly improved electro-optical and morphological characteristics. • Provides VALC systems for next-generation display technologies. Vertically aligned liquid crystal (VALC) perpetually boosts the advancement for display devices and optoelectronics. Herein, initially, the nanoparticles (NPs) induced VALC (nVALC) cell was prepared via doping of 0.3 (wt./wt.%) of zinc oxide NPs in nematic liquid crystal (LC). After that, a series of orange azo dichroic dye doped nVALC cells were prepared with varying concentrations of dye such as 0.0625, 0.125, 0.25 and 0.5 wt.%. The effect of dye concentrations on LC textures, phase transition, electro-optical and band gap properties were investigated, as well as resulted in a significantly reduced value of the threshold and operating voltages as a function of dye concentrations. The contrast ratio was also enhanced up to 0.25 wt.% dye doped nVALC cells. Additionally, the transition temperature from nematic to isotropic phase and band gap studies were also performed. The present work provides improved properties of nVALC systems for next-generation display technologies. [ABSTRACT FROM AUTHOR]

Porous carbon nanoparticles (PCNPs) of four different sizes (~180 nm, ~51 nm, ~41 and ~25 nm) were dispersed into a nematic liquid crystal (NLC) in 0.25 wt% concentration. PCNPs were derived from biowaste materials and pyrolysed at elevated temperatures to get the porous structure. Polarising optical microscopic observations were carried out in dark and bright states on both the pure NLC as well as NLC-PCNPs composites. Homogeneous alignment was well maintained in all the composites except the one with the highest sized (~180 nm) PCNPs. Birefringence, relative permittivity and dielectric anisotropy, increases as the size of the PCNPs is decreased in the composites. The threshold voltage was also found to decrease with the decrease in the size of the PCNPs. Such investigations may be useful for the fabrication of display devices such as flat panel displays (FPDs) and phase shifters. [ABSTRACT FROM AUTHOR]

We analyzed a Mach–Zehnder electro-optical modulator based on a silicon nitride strip–loaded waveguide on 0.5 μm thick x-cut lithium niobate thin film. The optical and radio frequency parameters for two different modulator structures (Type I: packaged with 2 μm thick SiO2 and Type II: unpackaged) were simulated, calculated, and optimized. The Optical parameters included the single-mode conditions, effective indices, the separation distance between the electrode edge and the Si3N4-strip-loaded edge, optical power distribution, bending loss, optical field distribution, and half-wave voltage. The radio frequency parameters included the characteristic impedance, attenuation constant, radio frequency effective index, and −3 dB modulation bandwidth. According to the numerical simulation and theoretical analysis, the half-wave voltage product and the −3 dB modulation bandwidth were, respectively, 2.85 V·cm and 0.4 THz for Type I modulator, and 2.33 V·cm and 1.26 THz for Type II modulator, with a device length of 3 mm. [ABSTRACT FROM AUTHOR]

Liquid crystals (LCs) have become indispensable materials in everyday life, with their applications ranging from high-resolution television displays to being a part of sophisticated and modern equipment for telecommunications and sensing purposes. Various important features of LC-based devices such as their response time, driving voltage, contrast ratio and brightness are controlled by the uniform alignment of the constituting molecules along the substrate surface. This alignment control can be achieved through various mechanical and non-mechanical techniques. Nanoparticles (NPs), which have become an underbelly of the latest technological developments, can also be incorporated into these tunable materials in order to achieve the desired alignment in them. The present review highlights the advantages of NPs -induced alignment technique over the other contemporary techniques available for aligning LCs. The NPs-induced alignment process is found to be cost-effective and reliable, and it does not require extreme physical conditions such as a low pressure for its operation. This alignment process enables manufacturers to effectively control the pretilt angle of the LC molecules by simply varying the concentration of the doped NPs in the host LC matrix. Furthermore, the alignment behavior in LCs is found to be a function of shape, size, concentration and solubility of the doped NPs in these materials. At the end, this review focuses on the methodology of developing new innovative devices based on this alignment process. With the fabrication of new NPs of different morphologies in recent times, the horizon of the LC nanoscience field is continuously increasing, thus paving way for new devices capitalizing on this alignment technique. [ABSTRACT FROM AUTHOR]

In this work, we have investigated morphological, electro-optical and dielectric properties of disperse orange 25 dye-doped polymer-dispersed liquid crystal (DPDLC) films. The DPDLC film composed of monomer Norland optical adhesive (NOA 65), nematic liquid crystal (E7), and disperse orange 25 dye was prepared through the polymerisation-induced phase separation (PIPS) method. The polarising optical microscope (POM) has been utilised to observe the effect of dye concentration and voltage on liquid crystal (LC) droplet morphology. The electro-optical properties of such DPDLC films were studied at a fixed frequency of 200 Hz and different voltage and temperature conditions (0–100 V, 25–50°C). The change in absorbance value with varying dye concentration and the electric field was monitored through a UV-Vis spectrophotometer. Dielectric relaxation characteristics of DPDLC films were examined using a precision impedance analyser in the frequency range 20 Hz–20 MHz and temperature range 25–60°C. Debye and Cole-Cole fitting techniques were used to describe the dielectric properties of DPDLC films. [ABSTRACT FROM AUTHOR]

• We demonstrate an electro-optically Q-switched Tm laser with constant short pulse duration of sub-25 ns at high PRFs ranging from 75 kHz to 150 kHz. • Maximum power of 22.4 W at 1936.8 nm is obtained at 75 kHz, with average duration of 21 ns and a deviation below 0.8 ns, corresponding to a peak power of 14.2 kW. • The results provide an efficient way to achieve constant short nanosecond pulse in high-power Q-switched Tm lasers. Conventionally, pulse duration of Q-switched lasers changes dynamically with the lasing power and pulse repetition frequency (PRF). Especially in quasi-three level Tm lasers, owing to the small emission cross section, they should oscillate at a PRF of below 50 kHz for a short Q-switching pulse that generally limited at tens of nanosecond. In this paper, we demonstrate an unprecedented electro-optically Q-switching scheme with constant short pulse duration of sub-25 ns at high PRFs ranging from 75 kHz to 150 kHz. Maximum average output power of 22.4 W at 1936.8 nm is obtained at 75 kHz, where average pulse duration of 21 ns with a deviation below 0.8 ns is realized during the whole Q-switching process, corresponding to a maximum peak power of 14.2 kW. The results provide an efficient way to achieve constant short nanosecond pulse in the high-power Q-switched Tm lasers, which could work at a PRF of above 100 kHz and facilitate a variety of appealing applications in material processing, surgery, and nonlinear frequency conversion toward the mid- and far-infrared regions. [ABSTRACT FROM AUTHOR]

Multimodal fusion approaches that combine data from dissimilar sensors can better exploit human-like reasoning and strategies for situational awareness. The performance of a six-layer convolutional neural network (CNN) and an 18-layer ResNet architecture are compared for a variety of fusion methods using synthetic aperture radar (SAR) and electro-optical (EO) imagery to classify military targets. The dataset used is the Synthetic and Measured Paired Labeled Experiment (SAMPLE) dataset, using both original measured SAR data and synthetic EO data. We compare the classification performance of both networks using the data modalities individually, feature level fusion, decision level fusion, and using a novel fusion method based on the three RGB-input channels of a residual neural network (ResNet). In the proposed input channel fusion method, the SAR and the EO imagery are separately fed to each of the three input channels, while the third channel is fed a zero vector. It is found that the input channel fusion method using ResNet was able to consistently perform to a higher classification accuracy in every equivalent scenario.

The present work reported the synthesis and characterisation of β-cyclodextrin (βCD) grafted into silica (SiO2@βCD) nanoparticles (NPs). Morphology analysis shows that the prepared NPs have a spherical shape with 170 nm of size. The electro-optic, dielectric and viscoelastic properties of SiO2@βCD doped nematic 5CB were examined in different concentrations of the NPs. A decrease in clearing temperature, birefringence and the order of the nanocomposite systems as compared to the pure system was observed. Dielectric parameters of pure and doped samples were measured in the frequency range of 1–2 MHz. Ionic conductivity and dielectric anisotropy increase significantly with NPs concentration due to the strong dipole moment and polarisability of SiO2@βCD. The advantage of dopedSiO2@βCDnematic 5CB is attributed to the significant decrements in threshold voltage by 32% and strong additional coupling of the electrical dipole moments in the spherical NPs with the nematic director field. On the other hand, it is found that the NPs exhibit a decreasing effect on the response time of the nematic liquid crystal, which is demonstrated by the decrement in the viscosity. The results indicate that doping SiO2@βCD is appropriate to fabricate a fast response LC device. [ABSTRACT FROM AUTHOR]

In this work, polymer dispersed liquid crystal (PDLC) films, with good electro-optical and adhesion properties, were obtained by phase separation induced through thiol-ene click chemistry. The effects of liquid crystal content, thiol content and thiol functionality on the electro-optical and adhesion properties of the PDLC films were systematically investigated. It is found that adding an appropriate proportion of high-molecular-weight polymer thiol, Capcure 3–800 as the curing agent can effectively decrease the saturation voltage of the PDLC films. And when the content of Capcure 3–800 is 5.5 wt.%, the PDLC films can show the optimised electro-optical performance. Moreover, the adhesion properties between the two pieces of substrates and the PDLC films are related to the density of the polymer network. [ABSTRACT FROM AUTHOR]

Aging is still the most challenging issue for organic light‐emitting diodes (OLEDs), which causes the image‐sticking artifacts on active‐matrix organic light‐emitting diode (AMOLED) displays and limits their lifetime. To overcome this demerit, an aging model is necessary to compensate for aging artifacts. In this paper, we present a unified OLED aging model, which combines three feasible modeling approaches of OLED degradation, namely, data‐counting, electro‐optical, and correlation methods. The model can be used to predict the efficiency decay of OLED pixels during operation. It mitigates weaknesses and limitations of each of these three models and deploys their strengths, respectively. In the first aging stage, the data‐counting model is prioritized, and in the later stages, it is calibrated using the correlation model. The dependency of the efficiency decay on the operation point of OLED is covered by the electro‐optical model. The unified model is based on both phenomenal and physical effects. It delivers more reliability to determine an OLED's degradation over a long‐term operation and a wide operation range like current amplitude and/or temperature range. The unified aging model applies to either an analog or a digital driving scheme. A corresponding compensation based on the aging model can be applied for extending the AMOLED lifetime. [ABSTRACT FROM AUTHOR]

In this article, we have performed ab-initio study on the homologues of 4-n-alkoxy-4′-cynobiphenyl (nOCB) series (n = 1–12) using DFT/B3LYP/6-31G(d,p) method. The Raman and UV-vis spectra of nOCB molecules have been analysed using DFT and ZINDO methods respectively. The dependence of electro-optical parameters such as dipole moment, mean polarizability, anisotropy in polarizability and molar refractivity along with global descriptors such as ionization potential, electron affinity, electronegativity, chemical hardness and electrophilicity index on the number of carbon atoms in the alkoxy chain has been examined. Also the variation of thermal parameters with the alkoxy chain length has been analysed. Electro-optical, electronic and thermal properties of nOCB LC molecules (n = 1–12) have been elaborated. [ABSTRACT FROM AUTHOR]

The present work reported the synthesis and the characterisation of laterally fluorinated handed bond liquid crystals (HBLCs) prepared by intermolecular hydrogen bonds between 4-pentyl-4-biphenylcarbonitrile (5CB) and 4-(nonyloxy)-3-fluoro benzoic acid (9OBAF). This compound-denoted 9OBAF-5CB was characterised by Fourier transform infrared spectroscopy (FTIR) and their mesomorphic properties were studied by polarising optical microscope (POM) and differential scanning calorimetry (DSC). Moreover, this compound shows a wide nematic phase with relatively high birefringence ( Δ n = 0.24 , modest dielectric anisotropy Δ ε = 5 , low viscosity (γ = 182.9 mPas). The enhancement of these parameters compared to that in individual compounds (9OBAF) and 5CB was obtained and discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Doping effect of functionalized CdSe/ZnS QDs on the characteristics of 8OCB LC was investigated. • Mobility of ions and diffusion constant were analyzed by a model based on the electrode polarization phenomenon. • Addition of QDs improved ion transport behavior by decreasing the electrode polarization relaxation time. • The threshold voltage drops remarkably with increasing QDs concentration in the LC system. • When the applied field is turned off, the doped samples exhibit a residual transmittance. The current advancements in developing new liquid crystalline materials for the next generation applications focus mainly on improving the physical characteristics of the liquid crystal (LC) systems. Recent progress has shown that the functionalized nanoparticles embedded in LC matrices can significantly alter the characteristics of the LC material based on the mutual interaction between the host molecules and guest particles. In this aspect, the present study reports the impact of dispersing core-shell type CdSe/ZnS quantum dots (QDs) on the dielectric, electrical and electro-optical properties of the 8OCB LC doped at various concentrations. The doped samples exhibit an ion releasing behavior and this effect becomes more evident as the doping concentration increases up to 0.2 wt% in the LC system. It is explained as a result of the growing tactoid-like ellipsoidal form acquired by QDs owing to the enhanced mutual interaction among QD ligands and rod-like LC molecules. The temperature variation of the diffusion constant, conductivity, ionic mobility and mean relaxation time of ions significantly follows each other in all the studied samples. Moreover, thermal profiles of the dielectric anisotropy, threshold voltage and splay elastic constant show a decreasing pattern with an increment in doping concentration. A dual-relaxation regime is experimentally investigated, corresponding to the contribution of nematic director and dimers, providing two kinds of rotational viscosity in the pristine and QDs dispersed LC samples. The transmittance-voltage curve reveals the presence of residual value in the dispersed samples and is related to the volatile memory effect. A slight enhancement is observed in the photoluminescence intensity for the lower doped sample and reduces further with increasing doping concentration in the pristine LC system. All these findings suggest the considerable contribution of functionalized QDs to the studied properties in terms of interaction between the LC and dopant material. This study will further elucidate the selection of optimal QDs concentration based on the required properties for their potential applications in futuristic devices based on LCs. [ABSTRACT FROM AUTHOR]

We analyzed a Mach–Zehnder electro-optical modulator based on a silicon nitride strip–loaded waveguide on 0.5 μm thick x-cut lithium niobate thin film. The optical and radio frequency parameters for two different modulator structures (Type I: packaged with 2 μm thick SiO2 and Type II: unpackaged) were simulated, calculated, and optimized. The Optical parameters included the single-mode conditions, effective indices, the separation distance between the electrode edge and the Si3N4-strip-loaded edge, optical power distribution, bending loss, optical field distribution, and half-wave voltage. The radio frequency parameters included the characteristic impedance, attenuation constant, radio frequency effective index, and −3 dB modulation bandwidth. According to the numerical simulation and theoretical analysis, the half-wave voltage product and the −3 dB modulation bandwidth were, respectively, 2.85 V·cm and 0.4 THz for Type I modulator, and 2.33 V·cm and 1.26 THz for Type II modulator, with a device length of 3 mm.

In this study, pure and doped ZnO thin films were prepared by sol–gel-based method and their electro-optical properties were investigated. For doping process, 1 at. % Al and Cu was incorporated in ZnO solution separately, and the thin films were prepared by dip coating method. The microstructure and morphology of calcined ZnO, Al-doped ZnO, and Cu-doped ZnO thin films were evaluated and compared by using various techniques X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and field emission scanning electron microscopy (FESEM). Results showed that nanostructured ZnO thin films with cross-linked nanoparticles (NPs) were formed, and the size of ZnO NPs increased with the Al and Cu doping. It was also found that the substitution and interstitial of Al and Cu dopants caused the instability of ZnO crystal structure and generation of extra point defects. Photoluminescence (PL) properties indicated that the dopants incorporation causes the decline of the PL intensity and the shift of the localized energy states of electrons and holes to lower energy levels. Evaluation of thin films in the UV–Vis range demonstrated that the transparency increased (>94%), and the band gap decreased to 3.08 and 3.06 eV with the incorporation of Al and Cu into ZnO thin films, respectively. The electrical conductivity also improved by Al and Cu doping of ZnO TFs. Highlights: Nanostructured sol-gel doped ZnO thin films show the promising electro-optical properties. Al and Cu dopant could change the parameters of ZnO lattice network. Optical band gap reduced by generation of point defects those act as luminescence quenchers. [ABSTRACT FROM AUTHOR]

The impact of the size of silica nanoparticles (SNPs) on the properties of ferroelectric liquid crystals (KCFLC 10R) has been investigated by electro-optical and dielectric techniques. We have found that the doping of silica nanoparticles in the host ferroelectric liquid crystal strongly affects the various properties of doped systems. Doping of silica nanoparticles shows a small decrease in spontaneous polarisation and faster switching time. An improvement in permittivity and conductivity with the temperature at a constant frequency was also noticed after dispersion. This dependence is stronger for large size particles ( ∼ 40 nm) and weaker for small size particles (~12 nm). The Goldstone mode (GM) shifts towards the higher relaxation frequency. These results would be useful to manufacture better optical and electronic devices for display, switching and beam steering applications. [ABSTRACT FROM AUTHOR]

A multifunctional material 0.65Ba 0.955 Yb 0.025 Er 0.005 TiO 3 –0.35CoFe 2 O 4 , owning superior piezoelectric, photoluminescence and magnetostrictive effects, was prepared via the conventional solid-state ceramic fabrication process. The ferroelectric, piezoelectric, dielectric, photoluminescence, as well as magnetic properties were characterized. Furthermore, in-situ magneto-electric, electro-photoluminescence and magneto-photoluminescence coupling effects were studied. A relatively larger magneto-electric coupling coefficient α E33 was determined to be 11 mV/Oe•cm@1 kHz, while the reversible electric and magnetic modulation ratio of integral intensity of green emission reached 16%@15 kV/cm and 2%@2 kOe, respectively. The underlying mechanism was discussed by PFM results, and the present work provides an alternative material to design devices with multiple functions. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Here, we present the effect of copper (II) oxide nanoparticles (nCuO) on dielectric and electro-optical parameters of a newly prepared ferroelectric liquid crystal (FLC) mixture, namely W302. The FLC mixture, comprising of pyrimidine compounds, was characterised through dielectric spectroscopy, differential scanning calorimetry (DSC), polarising optical microscopy (POM) and other electro-optical methods. The material parameters such as spontaneous polarisation, rotational viscosity, response time and tilt angle of W302 were found to be 14 nC/cm2, 240 mPa.s, 150 µs and 28ᴼ, respectively. The phase transition temperatures of W302 were observed through DSC and further confirmed by the dependence of dielectric loss factor in homogeneously aligned FLC sample with temperature. We also demonstrate the observance of a low-frequency dielectric relaxation mode due to the unwinding of the helix, called as partially unwound helical mode (p-UHM) along with Goldstone mode. The behaviour of p-UHM has been systematically studied with temperature and applied bias field. Further, dispersion of nCuO into host W302 has shown a significant increase in dielectric permittivity. Also, the p-UHM relaxation peak in the dielectric regime has disappeared with the incorporation of nCuO. These studies would be useful to fabricate better electro-optical devices for display, switching and beam steering applications. The formulation and characterization of a ferroelectric liquid crystal (FLC) mixture W302 composed of pyrimidine compounds is presented. Then, we observed the effect of copper (II) oxide nanoparticles (nCuO) on dielectric and electro-optical parameters of a newly prepared and characterized FLC mixture. [ABSTRACT FROM AUTHOR]

• We propose the multilayer film structure can modulate visible and IR light independently. • The fully-connected network with position coding shortens simulation time while maintaining accurate computation. • The designed structure is independent of polarization, easy to fabricate, and promising for future smart window applications. Electrochromic windows regulate the transmission and absorption of sunlight according to environmental conditions and personal preferences, resulting in energy conservation. However, developing smart windows that can independently modulate visible and infrared (IR) radiation remains a significant challenge. This paper presents a multilayer film structure for electrochromic windows based on the electro-optic dielectric material of 4-dimethyl-amino-N-methyl-4-stilbazoliumtosylate (DAST), and the film modulates visible and IR light individually. The refractive indices of multilayer DAST films change when different bias voltages are applied, which alters the structure's impedance and selectively modulates electromagnetic wave transmission. Simulation results indicate that the smart window can independently modulate the integrated visible transmittance (T vis) and integrated infrared transmittance (T IR) at four different bias voltages (-20 V to + 20 V). The modulation ranges for T vis and T IR are 72.5% to 92.3% and 46.1% to 95.2%, respectively, and the theoretical results surpass those of recent works. A fully-connected network with position coding is employed here, and simulation time is reduced based on truth prediction data. The multilayer structure proposed enables independent modulation of visible and IR light, making it a promising candidate for smart windows since it is lithography-free, large-area compatible, and polarization-independent. [ABSTRACT FROM AUTHOR]

A paradigm for high-quality factor (Q) with a substantial fulfillment for appraising sensing ability and performance has been investigated. Through constructing a 1D (one-dimensional) topological photonic crystal (PhC) mirror heterostructure, which is formed by the image view of 1D topological PhC stacking with its original one. In the 1D topological PhC-mirror heterostructure, there is an interesting mode that appeared with the symmetric, typical Lorentzian-line shape with 100% transmittance in the topological mirror edge-state mode (hybrid resonance mode) at the heterostructure interface. Physically, such a mode is a defect mode, but the defect is introduced through topological operations. The high Q-factor of 5.08 × 104 is obtained due to the strong optical localization of the defect mode at the topological edge area. Consequently, this device acts as a narrow passband filter. Moreover, due to the narrow bandpass property, it may be an advantageous reference for many applications in filtering, switching, and sensing. Thus, introducing an electro-optical (EO) polymer layer at the interface to modify the edge defect can tune the defect mode both in frequency and Q-factor for higher spatial pulse compression and higher EO sensitivity. Accordingly, the Q-factor of 105, the sensitivity of 616 nm/RIU, and the figure of merit of 49,677.42 RIU−1 are obtained. The sensing ability and performance are attributable to the strong optical localization in the interface region and enhanced light-matter interaction. We predict that the 1D topological PhC mirror heterostructure will be an outstanding point in the field of optical sensing, filters, and optical switching in different fields.

With the increasing sensitivity and accuracy of contemporary high-performance electronic information systems to electromagnetic energy, they are also very vulnerable to be damaged by high-energy electromagnetic fields. In this work, an all-dielectric electromagnetic field sensor is proposed based on a microring resonator structure. The sensor is designed to work at 35 GHz RF field using a lithium niobate-on-insulator (LNOI) material system. The 2.5-D variational finite difference time domain (varFDTD) and finite difference eigenmode (FDE) methods are utilized to analyze the single-mode condition, bending loss, as well as the transmission loss to achieve optimized waveguide dimensions. In order to obtain higher sensitivity, the quality factor (Q-factor) of the microring resonator is optimized to be 106 with the total ring circumference of 3766.59 μm. The lithium niobate layer is adopted in z-cut direction to utilize TM mode in the proposed all-dielectric electric field sensor, and with the help of the periodically poled lithium niobate (PPLN) technology, the electro-optic (EO) tunability of the device is enhanced to 48 pm·μm/V.

One of the main research activities of the Sol-Gel Group@ICMM (GSG-ICMM) is devoted to smart photonic materials derived from the incorporation of optically active substances in glasses. Those smart materials allow the control of their optical properties by applying external stimuli (e.g., electric field). That is the case of gel-glass dispersed liquid crystals (GDLC), where a sol-gel derived matrix with large porosity and embedded with liquid crystal (LC), forms a thin film between transparent conductive substrates needed to apply the electric field. The dielectric anisotropy of the LC permits the reorientation of the encapsulated LC by means of electric fields, enabling the control of its light transmission properties, from opaque (scattering) to transparent states. A different route to obtain LC dispersion devices was designed, taking advantage of biological structures created by bacterial activity. In this case, biofilms of the bacterium Pseudomonas putida mt-2 were grown on transparent conductive substrates from microbiological culture media. The chemical composition and the tridimensional porous structure of the biofilm enabled its use as a biological template for a LC dispersion device, where the LC is embedded in the biofilm porosity. The electrical control of the light transmission properties of these devices was carried out by applying electric fields. This new and non-chemical strategy expanded the possibilities for creating smart photonic materials by using bacterial cell factories. In the same topic of materials for the smart control of light transmission, a new concept was stablished to obtain an optical thin film material that exhibits reversible humidity-responsive transmittance. This material consists on a porous structure, with embedded hygroscopic and deliquescent compounds, having light scattering properties that depend on the humidity of the air in contact with the material. With dry air the material displays an opaque state due to light scattering. When exposed to humid air, the material scavenges water from the air, filling up its porosity with water and becoming transparent to the incident light. Upon exposure to dry air, water is released from the thin film material, recovering its previous light scattering state. The developed thin films can change their transparency when exposed to air with different relative humidity (RH), adjusting the light throughput. Therefore, this material concept can be used to design new optical devices, having the advantage that they do not require LC, transparent conductive glass substrates or complex layer-by-layer architectures for operation as in conventional smart windows. Smart control of light transmission, a new concept was stablished to obtain an optical thin film material that exhibits reversible humidity-responsive transmittance. [ABSTRACT FROM AUTHOR]

Cholesteric liquid crystal (CLC) compound present in egg yolk is extracted and characterized by polarized optical microscope, differential scanning calorimetry, scanning electron microscopy, dynamic light scattering and electro-optical measurements, confirming its potential use as an active material in the fields such as flexible liquid crystal displays. Emulsion polymerization is used to fabricate a flexible polyurethane shell with different thicknesses over CLC nanoparticles. Finally, thin films of prepared core-shell nanoparticles and poly(vinyl alcohol) as the binder are fabricated on the indium tin oxide substrates via knife-coating method and their electro-optical properties are evaluated. The films responded to applied potentials (4-18 V) by a 46-100% change in transmittance levels. The high shell thickness (5-45 nm) caused the need for higher voltages, because of the difficulty in feeling of the external field by liquid crystal (LC) core through the polymer shell. In the case of very thin or no polymer shell, the LC core becomes damaged or deformed under the electric field. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we promote a new polymer microsphere-filled cholesteric-liquid crystal (PFLC) system sandwiched between two flexible substrates for making a robust composite film with both bistable optical performance and high mechanical strength. The effects of the size of the polymer microspheres (PMs) and the pitch of the cholesteric liquid crystals (ChLCs) on the electro-optical performance of the as-made PFLC films were systematically investigated. Results show that the optical appearance of the optimized PFLC film can be reversibly changed between transparent and light-scattering states according to electric field by switching the ChLCs between planar (P) and focal conic (FC) states. Moreover, both P and FC states are stable for more than one year after removing the electric field, which is due to the great reduced polymer specific surface area of 1.78 m2/g and the spatial hindrance from the in situ thermally polymerized PMs, respectively. Aside from the long-term optical stability, the high content of the densely packed PMs also endows the PFLC film with a satisfactory shearing strength of 206.0 kPa between the top and bottom substrates, showing great potential applications in a wide range of uses, such as smart windows, electronic paper or writing tablets. Graphical abstract Unlabelled Image Highlights • A new in situ polymer microsphere-filled liquid crystal (PFLC) system was promoted for the first time. • The as-made PFLC film not only exhibits bistable electro-optical performance, but also high mechanical strength. • A comparative study was carried out to distinguish the PFLC system from the other two counterparts—PDLC and PSLC system. • The size of the polymer microspheres (PMs) in PFLC could be regulated from 4.86 μm to 9.62 μm using different compositions. • The relationships between the electro-optical properties and the size of the PMs / the pitch of the LCs were established. [ABSTRACT FROM AUTHOR]

We have prepared the composites of a room temperature nematic liquid crystalline material namely 4-(trans-4′-n-hexylcyclohexyl) isothiocyanatobenzoate (6CHBT) and gold nanoparticles (GNPs). Thermodynamic, electro-optical and dielectric properties have been investigated. Effect of dispersion of GNPs on various electro-optical and display parameters of host liquid crystalline material have been studied. Physical parameters such as threshold voltage, dielectric anisotropy and splay elastic constant have altered for composite systems. Due to the dispersion of GNPs, nematic to isotropic transition temperature is significantly increased. Relaxation frequency corresponding to flip-flop motion of the 6CHBT molecules about their short axes has increased due to the presence of GNPs. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of the 'Carol I' National Defence University / Buletinul Universitatii Nationale de Aparare 'Carol I' is the property of Carol I National Defence University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Bulletin of the 'Carol I' National Defence University / Buletinul Universitatii Nationale de Aparare 'Carol I' is the property of Carol I National Defence University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This publication introduces (spectral) photon emission (PEM) and electro-optical frequency mapping (EOFM/LVI) measurements to analog circuit elements (simple, cascode and low-voltage current mirrors). Different operating conditions of the devices are probed and the voltage dependence of the signals is analyzed. Results partly show close similarities to optical probing of digital IC's, but also differences in voltage dependence and signal levels due to more complicated voltage and signal distributions along the devices. [ABSTRACT FROM AUTHOR]

This paper provides lower bounds on the energy consumption and demonstrates an energy-time trade-off in optical computations. All the lower bounds are shown to have the matching upper bounds for a transitive function - shifting. Since the energy consumption in an optical transmission is a non-linear function of the distance, a new set of techniques was required to derive these lower bounds. We also characterize the energy requirements of 3-D VLSI computations. [ABSTRACT FROM AUTHOR]

The single-mode microring resonators on lithium niobate thin films were designed and simulated using 2.5-D variational finite difference time domain mode simulations from Lumerical mode Solutions. The single-mode conditions and the propagation losses of lithium niobate planar waveguide with different SiO2 cladding layer thicknesses were studied and compared systematically. The optimization of design parameters such as radii of microrings and gap sizes between channel and ring waveguides were determined. The key issues affecting the resonator design such as free spectral range and Quality Factor were discussed. The microring resonators had radius R = 20 μm, and their transmission spectrum had been tuned using the electro-optical effect.