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CuInS2/ZnS core/shell quantum dots (CIS/ZnS QDs) dispersed ferroelectric liquid crystal (FLC) mixtures have been characterized for their application in electro-optical devices, energy storage, and solar cells. Physical properties of the CIS/ZnS QD-FLC (ferroelectric liquid crystal) mixtures have also been investigated with varying QD concentrations in order to optimize the critical concentration of QDs in mixtures. The presence of QDs breaks the geometrical symmetry in the FLC matrix, which results in a change in the physical properties of the mixtures. We observed the reduced values of primary and secondary order parameters (tilt angle and spontaneous polarization, respectively) for mixtures, which also depend on the concentration of QDs. The reduction of spontaneous polarization in QDs-FLC mixtures is attributed to the adverse role of flexoelectric contribution in the mixtures. The 92% faster electro-optic response and enhanced capacitance indicate the possible application of these mixtures in electro-optical devices and solar cells. Photoluminescence emission of pure FLC and QDs-FLC mixtures has been thermally tailored, which is explained by suitable models. [ABSTRACT FROM AUTHOR]

Effects of luminescent coupling are observed in monolithic 5V, five-junction GaAs phototransducers. Power conversion efficiency was measured at 61.6%±3% under the continuous, monochromatic illumination for which they were designed. Modeling shows that photon recycling can account for up to 350mV of photovoltage in these devices. Drift-diffusion based simulations including a luminescent coupling term in the continuity equation show a broadening of the internal quantum efficiency curve which agrees well with experimental measurements. Luminescent coupling is shown to expand the spectral bandwidth of the phototransducer by a factor of at least 3.5 for devices with three or more junctions, even in cases where multiple absorption/emission events are required to transfer excess carriers into the limiting junction. We present a detailed description of the novel luminescent coupling modeling technique used to predict these performance enhancements. [ABSTRACT FROM AUTHOR]

Detailed investigations of the quadratic nonlinear response of a series of new polyimides with covalently attached chromophore DR13 are performed by the Maker fringes method in the range of fundamental wavelength from 850 to 1450 nm. Polymer films with thickness of 100–400 nm were spin-coated on glass substrates and corona poled. For these materials, the maximum values of the second harmonic generation coefficients d33 are 80-120 pm/V. A red shift of the nonlinear response dispersion with respect to the linear absorption spectrum was observed for the DR13 chromophore. The temperature dependences of linear absorption and nonlinear coefficients d33 for studied structures are observed. It was found that the temperature changes of the absorption spectra lead to appreciable contribution to the value of the nonlinear coefficient d33. The demonstrated high temperature stability (up to 120 °C) of chromophore-containing polyimide thin films makes it possible to eliminate the degradation of their nonlinear optical properties in the future applications of such structures. [ABSTRACT FROM AUTHOR]

We examine the excitonic properties of layered configurations of low dimensional transition metal dichalcogenides (LTMDCs) using the fractional dimensional space approach. The binding energies of the exciton, trion, and biexciton in LTMDCs of varying layers are analyzed, and linked to the dimensionality parameter α, which provides insight into critical electro-optical properties (relative oscillator strength, absorption spectrum, exciton-exciton interaction) of the material systems. The usefulness of α is highlighted by its independence of the physical mechanisms underlying the confinement effects of geometrical structures. Our estimates of the binding energies of exciton complexes for the monolayer configuration of transition metal dichalcogenides suggest a non-collinear structure for the trion and a positronium-molecule-like square structure for the biexciton. [ABSTRACT FROM AUTHOR]

A new method for measuring spin currents is proposed, based on the linear electro-optic (Pockels) effect caused by the additional second-order nonlinear electric susceptibility (electro-optic tensor) generated by the spin currents. The non-zero elements of electro-optic tensor induced by spin currents in GaAs crystal are calculated, and the wave coupling theory of linear electro-optic effect is used to analyze the polarization change of a probe beam. The numerical results show that, for a linearly polarized probe beam with a frequency close to the band gap of GaAs crystal, its polarization rotation can be as large as 14 lrad under an applied electric field of about 350V/mm. This effect should offer an alternative detection method for spintronics. [ABSTRACT FROM AUTHOR]

In a silicon-on-insulator (SOI) waveguide corner mirror (WCM) structure, with the quantum process of a frustrated total internal reflection (FTIR) phenomenon and the time delay principle in the two-dimensional potential barrier tunneling process of a mass of particles, we derive an accurate physical model for the Goos-Hanchen (GH) shift of optical guided-mode in the FTIR process, and in principle match the GH shift jumping states with the independent guided-modes. Then, we propose and demonstrate a new regime of 1 × N digital optical switches with a matching state between the free-carrier dispersion (FCD) based refractive index modulation (RIM) of silicon to create a GH shift jumping function of a photonic signal at the reflecting interface and the independent guided-modes in the FTIR process, where a MOS-capacitor type electro-optic modulation regime is proposed and discussed to realize an effective FCD-based RIM. At the critical matching state, i.e., the incident of an optical beam is at the vicinity of Brewster angle in the WCM, a mini-change of refractive index of waveguide material can cause a great jump of GH shift along the FTIR reflecting interface, and further a 1 × N digital optical switching process could be realized. For a 350-500 nm single-mode rib waveguide made on the 220 nm CMOS-compatible SOI substrate and with the FCD effect based RIM of silicon crystal, a concentration variation of 1018-1019 cm-3 has caused a 0.5-2.5 μm GH shift of reflected beam, which is at 2-5 times of a mode-size and hence radically convinces an optical switching function with a 1 × 3-1 × 10 scale. [ABSTRACT FROM AUTHOR]

Cholesteric liquid crystals with long pitch confined in homeotropic cells can be used to generate stable but distorted and localized liquid crystal structures exhibiting spherulitic textures, known as 'bubbles.' As these bubbles can be induced by an external electric field with a narrow range following the confinement ratio C=d/p ≈1 (d representing cell thickness and p representing cholesteric pitch), it is possible to obtain electrically controlled micro-lenses. Here we investigated the optical and electro-optical properties of such liquid crystal bubbles for creating an array of micro-lenses with electrically tunable focal length. [ABSTRACT FROM AUTHOR]

Deoxyribonucleic acid based gel solid electrolytes were prepared and their electric properties were characterized. Their ionic conductivity is in the range of 10-4-10-5 S/cm at room temperature and increases linearly in function of temperature, obeying an Arrhenius-like relationship. The present study, combined with the literature data, suggests that the electrical conduction mechanism in these membranes involve ion motion and/or charge hopping, promoted most likely by a significant interaction between the membrane components. The good conductivity results, as found here, together with the good transparency and good adhesion to the electrodes show that the DNA-based gel polymer electrolytes are very promising materials for application in various electrochromic devices. [ABSTRACT FROM AUTHOR]

It is shown that the formation of water at the surface of protonated LiNbO3 can lead to the precipitation of disordered phases, causing undesirable degradation of the electro-optic properties of the material. These structural defects are observed to increase the conductivity, which leads to a slow build-up of space charges, believed to be a key reason for voltage bias drifts in LiNbO3 electro-optic devices. Annealing under a controlled partial pressure of water vapor is shown to minimize such damage to the crystal lattice. An additional reverse exchange process is proposed that further improves the stability of the crystal and its electro-optic properties. [ABSTRACT FROM AUTHOR]

In order to estimate electro-optical response times, measurements of the transmitted light intensity through positive uniaxial nematic thin films in planar alignment have been performed. Very fast relaxation times were experimentally found for nematic samples aligned with conductive polymers, namely, polypyrrole doped with 5 types of anions having different molecular sizes and geometries. Using undoped polypyrrole alignment layers, slower electro-optical responses were obtained. Given that the improvement in the relaxation times is induced by the presence of the anions in the polypyrrole films, the increasing of the total restoring torque of the nematic molecules to the confining surfaces-responsible for the short relaxation times-is related to the charges accumulated at the nematic-conductive polymer interface. [ABSTRACT FROM AUTHOR]

We investigate the electro-optic properties and high-frequency relative dielectric constants of epitaxially grown lanthanum-modified lead zirconate titanate (PLZT) and polycrystalline barium titanate (BaTiO3) films in a high-frequency range of up to 40 GHz for designing a high-speed ferroelectric thin-film modulator. We also demonstrate a ferroelectric thin-film Mach-Zehnder-type waveguide modulator using the epitaxially grown PLZT film. The use of a composite structure with a low dielectric coefficient substrate and a buffer layer enabled of a ferroelectric thin-film waveguide modulator with 40-Gb/s operation. [ABSTRACT FROM AUTHOR]

Nanowires show a large potential for various electro-optical devices, such as light emitting diodes, solar cells, and nanowire lasers. We present a method developed to calculate the modal reflection and transmission matrix at the end facets of a waveguide of arbitrary cross-section, resulting in a generalized version of the Fresnel equations. The reflection can be conveniently computed using fast Fourier transforms once the waveguide modes are known. We demonstrate that the reflection coefficient is qualitatively described by two main parameters: the modal field confinement and the average Fresnel reflection of the plane waves constituting the waveguide mode. [ABSTRACT FROM AUTHOR]

We proposed a design of a tunable optical isolator. The electro-optic (EO) effects in periodically poled lithium niobate (PPLN) with a defect were studied. EO effects and second harmonic generation (SHG) allow three-wave coupling in this nonlinear optics process. A defect is inserted in an asymmetrical position in PPLN to break the reciprocity of the fundamental-wave transmission in two reversed propagating directions. We numerically demonstrated that the contrast of this optical isolator can be tuned from -1 to 1 by simply changing the external dc electric field. With EO effects, the position of the defect can be designed more flexibly maintaining a high contrast of the optical isolation. [ABSTRACT FROM AUTHOR]

Pb(ZrxTi1-x)O3 [x=0.52, PZT(52) near morphotropic phase boundary], tetragonal PZT(65), and rhombohedral PZT(20) thin films have been fabricated on different transparent substrates by radio frequency sputtering. The optical studies show that the band gap energies and refractive indices of the PZT thin films are crystal phase dependent. The largest electro-optic (EO) coefficient of 219.6 pm/V has been achieved by controlling the crystal phase of the PZT thin films. The linear EO coefficients of PZT(52) films on the (Pb0.86La0.14)TiO3-coated glass, indium tin oxides, and MgO substrates are also studied. Such study could contribute to the crystal phase and substrate dependent PZT films for electro-optic devices and multifunctional integrated circuits. [ABSTRACT FROM AUTHOR]

The CdGa2Se4 layers were grown by the hot-wall epitaxy method. From the absorption measurement, the band-gap variation in CdGa2Se4 was well interpreted using Varshni's equation. After the postannealing in various ambient, the behavior of point defects in CdGa2Se4 was investigated by measuring photoluminescence (PL). Point defects originating from VCd, VSe, Cdint, and/or Seint were classified as donor or acceptor types. Thus, the Ga in CdGa2Se4 did not form native defects because the Ga existed in the form of stable bonds in CdGa2Se4. Based on these PL results, we schemed out a band diagram of the recombination process in CdGa2Se4. [ABSTRACT FROM AUTHOR]

Planarly aligned cholesteric liquid crystals of short pitch were applied by the in-plane electric field. The reorientation of the director, increasing pitch, and flexoelectricity induce the change of transmission. The main effect in this research is due to the director reorientation along the electric field. The flexoelectricity deters the change in the birefringence induced by the dielectric response. The response was very fast for the effectively thin periodic boundary of the half-pitch of liquid crystal. The contrast ratio was more than 80 for red light and the response time was less than 0.1 ms for the experimental conditions. [ABSTRACT FROM AUTHOR]

In this paper we report the electro-optic characterization of two homologous series of low molar mass bimesogenic siloxane-containing liquid crystals. The materials used have two alkoxycyanobiphenyl mesogenic units with variable alkyl chain joined by a two- or five-siloxane moiety and all exhibit stable smectic A mesophases over wide temperature ranges (up to 100 °C wide). Due to their inherent ruggedness these materials have potential for use in polarizer-free, bistable, scattering display and storage devices. The bistable modes are at low and high frequencies. The low frequency mode (write) is a highly scattering focal conic texture resulting from electrohydrodynamic instabilities while the high frequency mode (erase) is a clear state due to dielectric reorientation of the material. Both modes are preserved upon removal of the applied electric field. We present threshold voltages as a function of temperature, frequency, and cell thickness and response times as a function of voltage for each of the bistable modes. We find reduced threshold voltages (5<=Vth<=12 V/μm) and response times that are strongly dependent on applied voltage (50 ms<=τ<=10 s). These operating conditions would suggest that these materials are particularly suitable for slow update, large area, low power information panels and displays. [ABSTRACT FROM AUTHOR]

ZnO thin films were epitaxially deposited on platinum/c-sapphire epitaxial layer using a radio frequency magnetron sputtering method. Xe, rather than Ar, was used as the sputtering gas. The leakage current as well as dielectric loss was suppressed upon use of Xe. Moreover, the full width at half maximum ω scan and surface morphology were improved by using Xe. These improvements are attributed to the fact that damage to the films during deposition using Xe is less than that upon the use of Ar. The electro-optical (EO) effect was evaluated by reflection configuration. ZnO films prepared with Ar showed no EO response. However, films prepared with Xe show a linear response of change in the birefringence with the electric field. The EO coefficient (rc) was evaluated as 0.2 pm/V. In order to reduce the leakage current and further improve the EO property, Mn was doped to the ZnO films prepared with Xe. As a result, the leakage current was eight orders of magnitude less than that of the undoped film. The dielectric loss was also reduced. Additionally, the frequency dispersion of dielectric loss was suppressed. Therefore, the space charge in the films is thought to be reduced by using Xe and doping with Mn. As a result of suppression of space charges, an rc of 2.2 pm/V was achieved. This value is close to that of the single crystal. [ABSTRACT FROM AUTHOR]

Responsivity measurements are reported for LiNbO3 electro-optic field sensors operated under applied electric fields at ac frequencies in the vicinity of the acoustic resonance values of the crystals. At these frequencies, piezoelectric effects dominate the sensor output. These resonance effects are well known and commonly considered parasitic. However, we propose their use as a sensitivity-enhancing mechanism for electric-field detection. We have found that our field sensors operated within these resonances responded linearly with the applied field strength and exhibited increases in their intrinsic sensitivities as high as 350 times larger than their normal, electro-optic values. Our modeling of the data suggests that the sensitivity enhancements are produced by the interplay between photoelastic shifts in the refractive indices and the physical vibration modes of the crystals. Aside from narrowband applications, these resonant enhancements can be exploited with fields at frequencies well beyond the narrow bandwidth of the acoustic resonance, if the fields are properly modulated. [ABSTRACT FROM AUTHOR]

The motion of highly dielectric polymer cholesteric liquid crystal (PCLC) flakes suspended in a host fluid can be controlled with an ac electric field. The electric field acts to induce a dipole moment on the flake due to interfacial, or Maxwell–Wagner, polarization. Theoretical modeling of PCLC flakes as oblate spheroids shows that the flakes will reorient to align one of the two major axes parallel to the electric field. The theory also supports the observed dependence of the particle reorientation time on the electric-field magnitude, frequency, and particle shape. A PCLC flake’s orientation determines its ability to reflect light of a specific wavelength and circular polarization. The ability to switch the position of PCLC flakes with an electric field has implications for electro-optic devices and display applications. [ABSTRACT FROM AUTHOR]

A Q-tensor method is used to model a grating-aligned zenithally bistable nematic device in two dimensions. The flexoelectrically driven switching between the two ground states is shown to occur through the creation and annihilation of pairs of defects, and the sign and magnitude of the voltage thresholds demonstrated to depend on the relative dielectric permittivity of the grating material. [ABSTRACT FROM AUTHOR]

The model of space-charge formation in photorefractive polymers due to Schildkraut and Buettner has been modified to include thermally accessible deep traps as well as shallow traps. The dynamic equations have been solved semiempirically using independent measurements of photoconductive properties to predict photorefractive dynamics. Dependencies of the dynamics on charge generation, mobility, trap density, acceptor density, ionized acceptor density, as well as their associated rates are examined. The magnitude of the fast time constant of photorefractive development is successfully predicted. The introduction of deep traps into the model has allowed us to qualitatively predict the reduction in speed due to deep trap filling and ionized acceptor growth. Experimental studies of photoconductivity and photorefraction (PR) in several polyvinyl carbazole photorefractive composites are carried out to demonstrate the applicability of the model. By choosing chromophores with different ionization potentials and by varying the chromophore concentrations, we investigate the influence of the chromophore ionization potential on the photoelectric and PR properties and reveal the nature of deep traps in the composites and their contribution to both photoconductivity and PR dynamics. Effects of plasticizer components are also discussed. [ABSTRACT FROM AUTHOR]

This article presents the results of an investigation of the electro-optical response for a hybrid twisted nematic (HTN) liquid crystal display. The device used both a hybrid alignment and a twisted director configuration. In comparison with the conventional twisted nematic mode, a faster response and a smaller operation voltage were obtained by using an appropriate amount of chiral dopant. The characteristics of the HTN cells were dependent on cell parameters such as the chemical nature of the polymer alignment layer, the cell thickness, the set twist angle, and the concentration of chiral dopant. Response times of 1.0 ms for turn-on and 16 ms for turn-off were achieved by the regulation of cell parameters. Computer simulations of the director configuration demonstrated that twist deformation plays an important role in the determination of the response characteristics. [ABSTRACT FROM AUTHOR]

Presents information on a study which proposed and demonstrated the design of an electrooptic polymer amplitude modulator. Technological steps for the fabrication of polymer-based devices; Concept of the polarization insensitive operation; Design and fabrication of the electrooptic polymer device; Conclusions.

Describes the electro-optical simulation of rotationally symmetric triode electron guns. Importance of computer aided design in the design of electron optical devices; Calculation of potential fields and trajectories; Development of a computer code for experimental verification.

Presents a study that focused on confocal interference microscope incorporating an electro-optic phase modulator has been used make simultaneous measurements of the inphase and quadrature components of the confocal signal as a reflecting surface is scanned axially, which is the V(z) response. Application of the V(z) technique in acoustic microscopy; Measured modulus and argument of V(z); Optical sectioning property of the confocal optical system.

Presents a study which examined the phenomenon of light propagation of birefringent medium with particular reference to the electro-optic crystal of Bi[sub 12]SiO[sub 20]. Electric field-induced linear birefringence for different crystal configurations; Polarization characteristics of the transmitted light; Measurement of the electro-optic coefficient.

Presents a study which developed an electro-optical technique to measure intense microwave. Principle of operation; Discussion of the proof-of-principle experiment; Data analysis.

Investigates the effects of asymmetric Fabry-Perot cavity structures on the switching dynamics of symmetric self-electro-optic effect devices made of AlxGa1-XAs/GaAs extremely shallow quantum wells. Response functions; Operating voltage and switching energies; Layer structure of a reflective-type optical modulator.

Presents a study which theoretically analyzed an electro-optical device consisting of a stack of undoped alternating layers of narrow- and wide-gap materials together with a series resistor under constant voltage bias. Operation of the device; Information on the Franz-Keldysh effect; Impact of the Kirchhoff's law for the electrical circuit of the device on the voltage drop; Mechanism for an effective operation of the devices.

Focuses on a study which investigated the dependence of electro-optic (e-o) effect in cubic materials on electric field distribution and light beam propagation direction. Derivation of the e-o effect in cubic materials using Nelson's approach; Methodology of the study; Results and discussion.

Focuses on a study which theoretically analyzed the multistable responses of two bistable elements optically connected in series. Model and equations; Types of possible multistable characteristics with respect to the wavelength of input light in the lower self-electro-optic devices; Illustration of the five cases of multistable characteristics obtained by the experiment.

Presents a study that proposed a type of silicon guided-wave electro-optic modulator. Use of the impact-ionization mechanism for carrier generation by the modulator; Electrical and wave propagation properties of the modulator; Attainment of numerical estimates of phase modulation due to refractive-index change.

Presents a study which analyzed the combined linear stress-optic and electro-optic effects in crystals of KDP-KD*lowast;P. Factor that lead to beam depolarization; Discussion on the electro- and stress-optic effects in KDP; Measurement of the transmitted wave-front distortion.

Presents a study which examined the measurement of the linear and quadratic electro-optic coefficients of GaAs at the wavelengths 1.32 and 1.52 µm using single-mode AlGaAs/GaAs strip-loaded waveguides. Status of quadratic electro-optic coefficients with increasing wavelength; Key components for telecommunications; Type of knowledge necessary to optimize the performance and behavior of the coefficients.

Presents a study that described the fabrication of directional couplers and Mach-Zehdner interferometers using electro-optic polymeric multilayer structures. Attractive features of side chain polymers as compared to other nonlinear materials; Considerations for the design of the switch diagram; Procedures in the fabrication of the devices.

Provides information on a study which calculated the effects of biaxial compressive and tensile strain on the excitonic resonances and associated changes in refractive index and electro-optic effect in quantum wells. Electro-optic properties of pseudomorphic quantum wells; Results and discussion; Conclusion.

Presents information on a study which examined the task of analyzing electro-optic properties of thin polymetric films by incorporating the films into the spacer layers of transmission-mode Fabry-Pérot devices formed using metal mirrors. Methodology of the study; Results; Conclusions.

Presents a study that determined the electro-optical coefficients of 2-methyl-4-nitroaniline (MNA). Focus on the development of materials capable of fast and efficient processing of optical signals; Description of crystal growing process; Details on the electro-optical capability of MNA; Design of the MNA phase modulator.

Examines the dynamics of grating formation in photovoltaic media. Formation of gratings with applied field; Processes that describe photorefraction in electro-optic crystals; Grating formation under open-circuit boundary condition; Importance of photorefractive crystals in optical information processing systems.

Presents a study that observed an electro-optic imaging of the internal fields in a gallium arsenide photoconductive switch. Applications of electro-optic sampling; Details on the optical imaging system; Discussion on the results of the study.

Presents a study that analyzed an all-optical integrated optics beam-scanning device. Features of the device; Analysis of the local nonlinearity of the device; Examination of the diffusive nonlinearity of the device.

Examines dielectric anisotropy and dielectric torque in ferroelectric liquid crystals and their importance for electro-optic device performance. Frequency dependence of the dielectric anisotropy; Measurements of the relevant anisotropic part of the dielectric constant for ferroelectric liquid crystals; Details of the capacitance and conductance measurements performed.

Presents a study that analyzed a structure of planar waveguide directional coupler/switch composed of gallium arsenide (GaAs)/AlGaAs. Background on the electro-optic directional coupler (EDC)/modulator; Examination of the operational characteristics of the proposed EDC/modulator in the AlGaAs-GaAs ternary system; Assessment of bandwidth and power consumption.

Presents information on a study which determined the director tilt angle, the layer-tilt angle, and the quiescent-state azimuthal angles of a surface-stabilized ferroelectric liquid-crystal cell as a function of temperature in the smectic C phase using electro-optical methods. Analysis of early experimental results on surface-stabilized ferroelectric liquid crystals; Methodology of the study; Results and discussion.

Presents a study which examined the novel structures for carrier-induced electro-optical phase modulation in crystalline silicon. Components of integrated-optics technology; Numerical estimation of carrier density enhancement for crystalline silicon; Conclusions.

Thermal dependent changes of light depolarization degree were observed in the SnO2:In2O3 (ITO) layers deposited onto the flat glass substrates which are used usually as electrodes for optoelectronic devices. The observed effect is reversible. It can be attributed to the changes of nanostructure geometry in the bulk of the ITO layer as well as on its surface. Such geometric changes involve dispersion of polarized light. The investigated effect should be taken into consideration when developing optoelectronic devices because it can provoke distortion of the optical information field. [ABSTRACT FROM AUTHOR]

A recently developed phase separated composite film method has been employed to fabricate a liquid crystal (LC) based electro-optical device using a single glass substrate. The resultant device is made of adjacent parallel layers of LC and polymer created by phase separation. The LC layer is confined between a film of solidified polymer layer on one side and the glass substrate on the other. Electro-optical properties of these devices demonstrate their technological potential in light weight and hand-held electronic products. [ABSTRACT FROM AUTHOR]

Examines the dynamic properties of a polar electro-optic effect in two surface states in a planar nematic liquid crystal. Discussion on how the difference in the anchorage and a bias direct current field affect the modulation efficiency as well as the relaxation times from the practical point of view; Effect of the disparity in the anchoring strengths on the flexoelectric relaxation.

Presents a study that examined the application of quantum-confined Stark effect observed in multiple quantum well (MQW) materials in electro-optic devices. Analysis of the electro-optic switching in the device; Examination of the intensity distribution between the waveguides of the device; Determination of the refractive index of the MQW.