Transverse Electro-optic Effect Research Articles

Optimization of transverse electro-optic effect in LiNbO3 and LiTaO3 crystals

Optimization of transverse electro-optic effect in LiNbO3 and LiTaO3 crystals

Amplitude electro-optical modulation of radiation by sequences of Fabry-Perot resonators

In this paper, we considered the method of amplitude electro-optical modulation of radiation using sequences of Fabry-Perot resonators based on the transverse electro-optical effect on the example of lithium niobate LiNbO3. With this method, it is possible to significantly reduce the voltage of the control electromagnetic field of the electro-optical amplitude modulator operating in the transmission mode of the light beam while maintaining its high efficiency. The reduction of the control voltage is achieved by increasing the number of Fabry-Perot resonators installed in series and the phase shift relative to the extremum of the transmittance function. This method allows to diminish the duration of the received light signals which leads to an increase in the clock frequency while maintaining a high efficiency of the radiation modulation. Diminishing the duration of light signals is achieved by using separate modulation channels of two sequences of electro-optical Fabry-Perot resonators, the first of which works on the transmission and the second one on the reflection. Increasing the clock frequency at the output of the modulator is achieved by summing the signals coming from several modulation channels. It is shown that the value of the control voltage for an amplitude electro-optical modulator based on a sequence of Fabry-Perot resonators made of lithium niobate LiNbO3, with an operating wavelength of 1.307 microns, can be 4 V in the case when its initial operating point corresponds to the maximum transmittance. The control voltage is 2 V if the initial operating point is shifted in phase relative to the extremum of the transmittance function.

Novel Fiber Optic Current Transformer With New Phase Modulation Method

Based on the transverse electro-optic effect of lithium niobate crystal, combined with polarizers and Faraday rotator, this paper presents a collinear closed-loop fiber optic current transformer with spatial non-reciprocity modulation method, and the feasibility of the scheme is verified by both the theoretical and experimental evidences. The detection scheme avoids the limitation of the transition time of the sensing fiber coil on the phase modulation frequency, improves the sensitivity and stability of the system, and reduces the volume and cost of fiber optic current transformer. The sawtooth wave modulation scheme is adopted to realize phase bias modulation and feedback modulation through phase shift of sawtooth wave to achieve closed-loop detection effect, which enhances the signal to noise ratio and simplifies demodulation mode. The experimental results show that the current ratio errors measured at room temperature range from 1% to 120% of rated current meet the requirements of national standard GB/T 20840.8-2007 and reach the accuracy level of 0.2S. The temperature stability of the current transformer is also tested, and the ratio error measured at the rated current does not exceed ±0.2% in the range of -30 °C to 50 °C.

REDUCTION OF THE CONTROL VOLTAGE IN THE AMPLITUDE ELECTROOPTIC MODULATOR AT MULTIPLE-INTERFERENCE IN A RING RESONATOR

In this paper, it’s described a method that allows to implement highly efficient amplitude modulation of radiation at the output of a ring resonator by controlling its artificial light losses, which are derived from it using two Y-shaped couplers. At the same time, the necessary constant level of light energy is provided in the resonator, which, due to the absence of radiation losses when entering it into the ring resonator, allows one to achieve a significantly lower value of the required control electric voltage than existing electro-optical modulators, and, therefore, a smaller amount of consumed electric power and an increase in working frequency range of modulation of optical radiation. The possibility of implementing the method under consideration is ensured by the fact that the input of light energy into the ring resonator can be carried out without loss, in addition, single-mode waveguides are able to maintain the temporal coherence of transmitted radiation, which ensures the implementation of multipath interference. The stabilization of the optical characteristics of a ring resonator, which is very sensitive to changes in various external factors, for example, temperature, pressure, vibrations, can be achieved by electro-optical correction of the length of the optical path of the resonator by introducing a controlled phase element operating on the transverse electro-optical effect into the ring resonator and implementing corresponding optoelectronic feedback circuit.

On-Chip Solc-Type Polarization Control and Wavelength Filtering Utilizing Periodically Poled Lithium Niobate on Insulator Ridge Waveguide

The state-of-the-art lithium niobate on insulator technology has enabled a variety of fascinating integrated functionalities. It combines versatile properties of lithium niobate and a high refractive index contrast of it with respect to silica or air for integrated photonic applications. Here, we present an on-chip Solc-type device based on transverse electro-optic effect at the telecommunication wavelengths in a periodically poled lithium niobate on insulator ridge waveguide. The efficient quasi-phase matched TE $\leftrightarrow$ TM mode converter controlled by transverse applied electric field at low voltages is demonstrated for both linear polarization rotation and wavelength filtering at fast modulation speed. This paper demonstrates promises for developing novel integrated devices on the new platform for polarization sensitive applications.

Phase-shifted Solc-type filter based on thin periodically poled lithium niobate in a reflective geometry.

Configurable narrow bandwidth filters are indispensable components in optical communication networks. Here, we present an easily-integrated compact tunable filtering based on polarization-coupling process in a thin periodically poled lithium niobate (PPLN) in a reflective geometry via the transverse electro-optic (EO) effect. The structure, composed of an in-line polarizer and a thinned PPLN chip, forms a phase-shift Solc-type filter with similar mechanism to defected Bragg gratings. The filtering effect can be dynamically switched on and off by a transverse electric filed. Analogy of electromagnetically induced transparency (EIT) transmission spectrum and electrically controllable group delay is experimentally observed. The mechanism features tunable center wavelength in a wide range with respect to temperature and tunable optical delay to the applied voltage, which may offer another way for optical tunable filters or delay lines.

Optical isolation based on Faraday-like effect in periodically poled lithium niobate with odd number of domains tailed with a semi-domain

We observe the phenomenon of the Faraday-like effect, which occurs in periodically poled lithium niobate with odd number of domains (OPPLN) by the transverse electro-optic (EO) effect under the quasi-phase-matching condition. In this case, light rotates in the reverse sense during the forward and the backward path, and OPPLN shows a nonreciprocal process that is similar to the magneto-optical Faraday effect, which has served as a routine method for achieving optical isolation. Therefore, a feasible scheme for an EO optical isolator based on the Faraday-like effect by adding an additional semi-domain to OPPLN is also proposed in this article.

Crystals modulated by two parameters and their applications

In the applications of two external fields, such as stresses and electric fields, the optical modulation properties of some crystals are theoretically analyzed using the method of index ellipsoid. Simple mathematical formulas for the calculations of the field-induced principal refractive indexes of some crystals and corresponding azimuthal angles of their principal axes can be deduced from the equation of index ellipsoid if there exists only one nonzero cross term in the equation, e.g. x1x2. According to these simple formulas, we can find out some crystals exhibiting dual transverse electrooptic effect, e.g. crystals of the 6 symmetry point group. Under two simultaneously applied external stresses, elastooptic birefringence of a crystal is proportional to the difference between the two external stresses, and the orientations of their birefringent axes are unchanged. When a stress and an electric field are simultaneously and perpendicularly applied to some crystals such as cubic crystals of 43m point group, the field-induced birefringence of the crystal is proportional to the weighted geometric mean of the applied stress and electric field, and the orientations of their birefringent axes only depend on the ratio of the applied electric field and stress. The above electrooptic and elastooptic modulation properties are useful to the design of novel optical modulators and sensors.

Group velocity control of femtosecond pulse in folded dielectric axes structures by electro-optic effect

Theoretical investigation on the group velocity control of ultra-fast pulses by transverse electro-optic effect as well as its cascading and cubic nonlinearity is presented. Numerical simulation shows that the group velocity can be tuned via conveniently modulating the external electric field strength or the intensity of input pulse. The response of group velocity modulation is in proportion to these two factors, and the advancement or delay can reach the magnitude of 1–2 fractional pulses, which could be a potential scheme for controlling the velocity of pulse in future high speed and large-capacity communication networks.

A heterodyne laser interferometer for dilatometer measurements

A dilatometer measuring system based on heterodyne laser interferometry is described. An electrooptical light modulator based on the double transverse Pockels electrooptical effect in a crystal of lithium niobate and operating in the quarter-wave mode is used as the optical heterodyne. The electronic measuring system uses modern microelectronic components with a high degree of integration.

Proposal for electro-optic multiplier based on dual transverse electro-optic Kerr effect

A novel electro-optic multiplier is proposed, which can perform voltage multiplication operation by use of the Kerr medium exhibiting dual transverse electro-optic Kerr effect. In this kind of Kerr medium, electro-optic phase retardation is proportional to the square of its applied electric field, and orientations of the field-induced birefringent axes are only related to the direction of the field. Based on this effect, we can design an electro-optic multiplier by selecting the crystals of 6/mmm, 432, and m3m classes and isotropic Kerr media such as glass. Simple calculation demonstrates that a kind of glass-ceramic material with a large Kerr constant can be used for the design of the proposed electro-optic multiplier.

Experimental investigation of optical beam deflection based on PLZT electro-optic ceramic

Based on the optical characteristics of PLZT (Lead Lanthanum Zirconate Titanate) electro-optic ceramic, two kinds of electro-optical deflectors, triangular electrode structure and optical phased array technology, are studied in detail by using transverse electro-optic effect. Theoretically, the electro-optic deflection characteristics and mechanisms of the deflectors are analyzed; experimentally, the optical characteristics of ceramic wafer, such as the phase modulation, the hysteresis and the electro-induced loss characteristics, are measured; a systematic experiment is designed to verify the theoretical results. The effect of temperature on the performance of deflector is also investigated. Comparing with both structure's deflectors, the optical phased array technology has a higher angle scanning resolution, however, it has a relative small deflection angle. OCIS codes: (230.2090) Electro-optical devices; (160.2100) Electro-optical materials; (060.5060) Phase modulation.

Modulation, alignment, and calibration methods for phase-modulated optical polarimeters

We have studied, assembled, and tested several different types of phase-modulated optical polarimeters capable of transient stress and molecular orientation angle measurements in complex optically anisotropic fluids and materials. The main difference in the instrumentation lies in the applied modulation technique. Three different phase modulation techniques are studied in this paper: the photoelastic effect, the transverse electro-optic effect, and liquid-crystal variable retardation modulation schemes. The precise measurement of a material's retardance and average molecular orientation angle depends on an accurate alignment and calibration within the range of the chosen modulator. Therefore, we address some of the issues associated with the choice of phase modulator as well as applicable alignment and calibration techniques. We also study and test several methods that may be used to ameliorate these issues.

Diffraction light modulator based on transverse electro-optic effect in short-pitch ferroelectric liquid crystals

A diffraction modulator that exploits the transverse electro-optic effect in ferroelectric liquid crystals is proposed for applications in displays and in spatial light modulators. Experiments with a short-pitch ferroelectric liquid crystal aligned homeotropically show an achromatic contrast ratio of greater than 100:1 available with oblique readout. The sources of the contrast deterioration and the tolerance of the proposed scheme to this deterioration are analyzed. For selected directions of readout the light output obtains low sensitivity to the polarization of the readout light. Nonlaser light sources can be used in a practical display setup based on the proposed principle.

Electric field selectivity of reflection volume holograms in LiNbO 3

Theoretical and experimental investigations of electric field selectivity of reflection volume holograms in the geometry of the transverse electro-optic effect in LiNbO 3 are presented. The orientation of the LiNbO 3 allowing one to optimize the electric field selectivity has been found. Seventeen holograms were recorded in various electric fields, which demonstrates the efficiency of electric field multiplexing.

Transverse electro-optic effect of antiferroelectric lead zirconate thin films

The transverse electro-optic effect in antiferroelectric lead zirconate thin films grown on fused quartz is observed. The birefringence shift as a function of the external electric field exhibits a characteristic response that is related to the electric-field-induced antiferroelectric-to-ferroelectric structural transition.

Analytical model for the quadratic electro-optic effect of perovskites.

A semiclassical model of the transverse electro-optic effects including both electronic and ionic contributions is proposed for perovskite materials. It is found that for perovskite structure the linear and the nonlinear susceptibilities are related via a single parameter of the material. Therefore, the model yields a formula that provides a semiquantitative prediction of the quadratic electro-optical coefficient of the materials from their indices of refraction and dielectric constants.

Growth of ferroelectric tungsten bronze crystals and thin films

Abstract In this paper, we review the state-of-art for the growth of ferroelectric tungsten bronze single crystals in optical quality and large size. The Czochralski technique has been optimized for various bronze solid solution crystals such as Sr1−xBaxNb2O6 (SBN), Ba2−xSrxK1−yNayNb5O15 (BSKNN) and Sr2−xCaxNaNb5O15 (SCNN) with properties specifically tailored for electro-optic, pyroelectnc and more recently for photorefractive applications. SBN solid solution crystals are found to be easiest to grow in series up to 1′′ in diameter with excellent transverse electro-optic effects; whereas BSKNN crystals, which exhibit excellent longitudinal electro-optic effects are more difficult to grow in large sizes and optical quality. BSKNN crystals exhibit ferroelectric and optical properties similar to perovskite BaTiO3 and are found to be particularly useful for photorefractive applications. The SCNN solid solution crystals are orthorhombic at room temperature and are much more difficult to grow; currently, crysta...

The evolution of the photoinduced space charge and electric field distribution in photorefractive sillenite (Bi12GeO20, Bi12SiO20) crystals

The paper reviews experimental and theoretical studies of the generation of photoinduced space charges and electric fields in sillenites. A. method is described of direct field distribution measurements on noncentrosymmetric crystals which is based on using the linear transverse electro-optic effect. The principal types of local centers and electronic transitions in sillenites are considered. Field evolution measurements are presented for various conditions of crystal photoexcitation. A theoretical discription is given of a sufficiently general charge transfer model involving the photogeneration of free carriers, their drift and trapping throughout the depth of the material. The calculations presented describe the field evolution under different conditions, in particular, for nonuniform carriers generation. The most interesting case is probably that of uniform generation which results in an unusual phenomenon, namely, space charge stratification under the screening of the external field. It consists in the formation of a multilayer variable-sign space charge structure with its layers moving against the carrier drift. The results of these studied may be used in the development of space-time light modulators and calculation of their characteristics.

Memory and dynamic imaging in a conducting PRIZ

The conducting PRIZ spatial light modulator, which uses transparent electrodes deposited directly onto the surface of a photorefractive crystal, has information storage times which are a strong function of the incident write-beam energy density. The memory or storage time has been found to be a monotonically decreasing function of the incident write-beam energy density. At low energy densities, the memory time is of the order of 0.5 h. However, at sufficiently high write-beam energy densities, the device acts as a differentiator and exhibits dynamic image selection. The optical output of the device, which depends upon the transverse electro-optic effect, peaks at moderate energy levels.