Measurement Of Electro-optic Coefficient Research Articles

Electro-optic coefficient measurement of a K(H1-xDx)2PO4 crystal based on χ(2) nonlinear optical technology.

We present a novel method utilizing the χ(2) nonlinear optical technology, which can realize high precision measurement of linear electro-optic (EO) coefficients of nonlinear materials. By applying the linear EO effect to the nonlinear optical process, the theoretical model of this measurement method was established, and the calculation formula of the linear EO coefficient was given. In the proof-of-principle experiment, by introducing an external electric field into the fourth harmonic generation (FHG) process, we comprehensively obtained the linear EO coefficients of K(H1-xDx)2PO4 crystals and revealed the relationship between deuterium content (x) and EO coefficient (γ63): γ63 = -9.789 - 16.53x. Meanwhile, the stability of FHG was greatly improved, and the angular range of efficiency stability was increased to 4.4 times in maximum. This work not only systematically demonstrates the FHG characteristics of KDP-family crystals, which provides a good reference for the deep ultraviolet laser generation, but also offers a new way to measure the basic parameters of nonlinear optical materials.

A powder method for the high-efficacy evaluation of electro-optic crystals.

The electro-optic crystal holds great promise for extensive applications in optoelectronics and optical communication. However, the discovery of novel electro-optic crystals is sporadic due to the difficulties of large-sized crystal growth for electro-optic coefficient measurement. Herein, to address this issue, a high-efficacy evaluation method using accessible powder samples is proposed in which the second-harmonic-generation effect, infrared reflectance spectrum and Raman spectrum are introduced to predict the magnitude of the electro-optic coefficient. The calculated electro-optic coefficients of numerous reported electro-optic crystals through this approach give universal agreement to the experimental values, evidencing the validity of the strategy. Based on this method, CsLiMoO4 is screened as a novel potential electro-optic crystal and a high-quality crystal is grown by the Czochralski technique for electro-optic coefficient measurement using the half-wave voltage method, the result of which is also comparable to the calculated value. Consequently, the evaluation strategy presented here will pave a new way to explore promising electro-optic crystals efficiently.

Communication—Electro-Optic Coefficient Measurement by Using Linearity between Refractive Index Change and Externally Applied Electric Field

We propose a method to measure electro-optic(EO) coefficient of either a bulk crystal or a thin-film or a planar/slab waveguide by using the linearity between refractive index change induced by EO effect and externally applied electric field. A LiNbO3 single-crystal is exemplified. By using prism coupling technique the EO-effect-induced refractive index change at crystal surface was measured vs electric field. By using their linearity the EO coefficient is determined. A comparison with previously reported values shows that the measured data can be considered as identical to the reported within the error, confirming feasibility of the method. The accuracy is ∼7%.

Measurement method of electro-optic coefficients using photoelastic modulation.

To realize high-speed, accurate, and sensitive measurement of electro-optic (EO) coefficients, a novel measurement method using photoelastic modulation is proposed. A simple polarimetry is constructed based on the photoelastic modulator, and the phase difference induced by the EO sample is loaded in the modulation signals. Employing the digital phase-locked technology, the DC, first, and second harmonic terms are extracted, respectively, and then the EO coefficients are demodulated. The experimental system is set up to analyze the principle of this scheme in detail. A Y-cut LiNbO3 crystal plate is selected as the sample, and the EO coefficient γ22 is studied under different applied DC voltages. The results demonstrate that the measurement accuracy and sensitivity of the system are 0.22% and 1.5×10-14 m/V, respectively, when the sampling time is set as 198.9ms. The measuring rate can be further enhanced, if the appropriate reduction of the measurement sensitivity is allowed.

Application of polarimetric technique for determining the sign of quadratic electro-optic coefficients in crystals

So-called polarimetric methods are based on measurements of the intensity of light emerging from a modulator composed of a “sandwich” of investigated crystal placed between polarizer and analyzer. The polarimetric technique is known for its high accuracy in determining absolute values of electro-optic coefficients; however, the method is considered unable to find their signs. In this paper, we propose an examination of changes in the modulated signal phase that result from a controlled shift through the transmission characteristic of the modulator. We show that analysis of the changes allows one to obtain the sign of the coefficients. The sensitivity of the method is examined in measurements of quadratic electro-optic coefficients. It is found that the technique may be easily applied to crystals for which relatively low values of the coefficients, i.e., of the order of magnitude 10−20 m2/V2, are observed. Configurations where the light beam is sent along the optical axis and perpendicularly to the axis in a uniaxial crystal are considered. Examples of measurements of the quadratic electro-optic coefficients g1111−g1122 in KDP and ne3g3333−no3g1133 in DKDP are presented.

Accurate measurement of electro-optic coefficients of undoped and MgO-doped stoichiometric LiNbO_3

We accurately measure the electro-optic (EO) coefficients of undoped and 1.7 mol% MgO-doped stoichiometric LiNbO3 (SLN) using high-quality crystals and a reliable AC-field applying method. The EO coefficients at the wavelength of 633 nm are determined to be r33 = 30.2 ± 0.6 pm/V and r13 = 9.1 ± 0.2 pm/V for undoped SLN, and r33 = 29.8 ± 0.2 pm/V and r13 = 9.1 ± 0.04 pm/V for MgO-doped SLN. The obtained values are found to be nearly the same with those for congruent LiNbO3.

弹光调制测晶体电光系数的数字锁相实现

弹光调制测晶体电光系数的数字锁相实现

弹光调制高灵敏测量晶体电光系数

弹光调制高灵敏测量晶体电光系数

Review and comparison of experimental techniques used for determination of thin film electro-optic coefficients

The results of electro-optic coefficient measurements performed with three commonly applied techniques used to assess electro-optic coefficients: the Mach–Zehnder, the Teng–Man, and the attenuated total reflectance technique are reported. It is shown that the signal obtained by the Mach–Zehnder and Teng–Man techniques is strongly influenced by the multiple internal reflection and piezo- and electrostrictive thickness change effects, which in our opinion have not been addressed sufficiently in the literature. A novel approach based on using Abelès matrix formalism is implemented for the retrieval of electro-optic coefficients from experimental data. The measurement results, errors, and comparison of the obtained electro-optic coefficient values with the ones expected from the second harmonic generation measurements are discussed. It is demonstrated that, by applying incidence angle scan measurements in Teng–Man technique, an analytic approximation that ignores multiple internal reflection and thickness change effects can provide an electro-optic coefficient estimate within the precision of 2%. This value is much less than the error caused by the thickness change effect that may appear in the attenuated total reflectance technique which inherently has low sensitivity to the thickness modulation effects in the sample.

Electro-optic Coefficient Measurement of the Double Electro-Optic Molecules Polymer based on Terahertz Application

In the terahertz (THz) science research field, electro-optic (EO) polymer possesses many superior characters compared with mineral crystal. Two kinds of the side group EO polymer, polyphosphazene with plmaol grained by 2, 4-dinitroaniline and polyphenylacrylate containing p-nitro bisazo group, are synthesized and characterized. For higher EO coefficient, the double EO molecules polymer thin films are prepared by mixing a small nonlinear optical (NLO) molecule into the side group EO polymer. The principles of preparation are given and the EO coefficients are tested. The effect on the EO coefficients by different mixing proportion and different poling temperature are analyzed in details. Experiments results show that the double EO molecules polymer has fine stability, higher EO coefficient and can be easily processed. This kind of material has the potential to be widely applied in the emission and detection of THz radiation.

Electro-optic and converse-piezoelectric properties of epitaxial GaN grown on silicon by metal-organic chemical vapor deposition

We report the measurement of the (r13, r33) Pockels electro-optic coefficients in a GaN thin film grown on a Si(111) substrate. The converse piezoelectric (d33) and electro-absorptive coefficients are simultaneously determined. Single crystalline GaN epitaxial layers were grown with a AlGaN buffer layer by metal organic chemical vapor deposition, and their structural and optical properties were systematically investigated. The electro-optic, converse piezoelectric, and electro-absorptive coefficients of the GaN layer are determined using an original method. A semi-transparent gold electrode is deposited on the top of the GaN layer, and an alternating voltage is applied between top and bottom electrodes. The coefficients are simultaneously and analytically determined from the measurement of the electric-field-induced variation ΔR(θ) in the reflectivity of the Au/GaN/buffer/Si stack, versus incident angle and light polarization. The method also enables to determine the GaN layer polarity. The results obtained for a Ga-face [0001] GaN layer when using a modulation frequency of 230 Hz are for the electro-optic coefficients r13 = +1.00 ± 0.02 pm/V, r33 = +1.60 ± 0.05 pm/V at 633 nm, and for the converse piezoelectric coefficient d33 = +4.59 ± 0.03 pm/V. The value measured for the electro-absorptive variation at 633 nm is Δko/ΔE = +0.77 ± 0.05 pm/V.

共面插指电极结构电光聚合物薄膜器件的电光系数测量

共面插指电极结构电光聚合物薄膜器件的电光系数测量

顺电相KLTN晶体Kerr系数和透射率的数字全息测量

顺电相KLTN晶体Kerr系数和透射率的数字全息测量

Electrooptic coefficient measurements by Mach Zehnder interferometric method: Application of Abelès matrix formalism for thin film polymeric sample description

In Mach–Zehnder interferometric (MZI) method for determination of thin organic film electrooptic (EO) coefficients r13 and r33 critical effects, like multiple internal reflections and sample thickness modulation due to electrostriction and piezoelectricity are usually overlooked. Ignoring these effects may lead to inaccurate calculation of EO coefficients from experimental data by the simplified equations. To describe the influence of the above mentioned effects on the output of a MZI containing a thin film polymer sample we have used the Abelès matrix formalism.

Wavelength dispersion measurement of electro-optic coefficients in the range of 520 to 930 nm in rubidium titanyl phosphate using spectral interferometry

Rubidium titanyl phosphate (RTP) is widely used for electro-optical applications at low switching voltages. RTP is nonhygroscopic and does not induce piezoelectric ringing up to the megahertz range. It has large electro-optic (EO) coefficients and a high damage threshold. We present here the EO coefficient wavelength dispersion measurements in the [550,950] nm spectral range using a method based on spectral interferometry. These data are necessary for, among other things, a quantitative modelization of an EO carrier-envelope phase shifter.

Zirconium-doped lithium niobate: photorefractive and electro-optical properties as a function of dopant concentration

Measurements of refractive indices, electro-optic coefficients and photorefractivity are performed for a set of Zirconium-doped congruent lithium niobate (Zr:LN) crystals as functions of the dopant concentration in the range 0.0-3.0 mol%. The photorefractive properties are studied by measuring the green-light induced birefringence change and by direct observation of the transmitted-beam distortion. The index of refraction data show that the threshold concentration, above which there is a change in the Zr incorporation mechanism, is about 2.0 mol%, but photorefractivity results suggest that the concentration of ZrO2 required to strongly reduce the photorefractive effect is somewhat larger than the 2.0 mol% “threshold” concentration derived from index-of-refraction data. The electro-optic coefficients are little influenced by Zr-doping. All the reported results confirm that Zr:LN is a very promising candidate for the realization of efficient electro-optic and all-optical nonlinear devices working at room temperature.

A method for compensating multiple-reflection effect in measurement of electro-optic coefficient

An electro-optic (EO) coefficient can be evaluated from a modulated signal by applying an AC voltage to a plane-parallel sample in an interferometer. We proposed a method for compensating multiple-reflection of a light in the sample. The multiple-reflection causes errors in the evaluated EO coefficient. In measurement using a Mach-Zehnder interferometer, we analyzed the multiple-reflection and clarified its unfavorable effect. The effect could be avoided simply by selecting the incidence angle of the light on the sample. We confirmed this by measuring the EO coefficient of a KTiOPO4 crystal.

Effect of Multiple Reflections on Accuracy of Electro-Optic Coefficient Measurements

The intensity of a detected beam, taking into account multiple reflections occurring on the surface of a crystal rod, for a Mach–Zehnder interferometer, a Michelson interferometer and a Senarmont polarimeter has been derived. Using the derived equations, we analyzed the effect of multiple reflections in terms of the number of reflections on the surface, the static phase, and the refractive indices as well as the reflectivity of the random uniaxial crystals. Through the simulations, to realize high accuracy measurement and obtain reliable results with a low driving voltage, the careful treatment of the electro-optic sample is necessary.

Measurement of electro-optic coefficients of 1.3 [micro sign]m self-assembled InAs/GaAs quantum dots

The electro-optic properties of 1.3 µm self-assembled InAs/GaAs quantum dots grown by metal organic chemical vapour deposition are reported. The linear and quadratic electro-optic coefficients are 2.4×10−11 m/V and 3.2×10−18 m2/V2, respectively, which are significantly larger than those of GaAs bulk materials. Also, the linear electro-optic coefficient is almost comparable to that of lithium niobate.

Determination of the crosslinking temperature of the thermally crosslinkable polyurethane by attenuated total reflection spectrum

An experimental technique is presented in this paper for the measurement of the crosslinking temperature (Tcrosslinking) of the polymer films by using the attenuated total reflection (ATR) spectrum. According to the change of the ATR spectrum, the changing value of the refractive index of the polymer film can be determined during the ascending temperature. Experimental results definitely show that the temperature dependence of the refractive index dn/dT changes discontinuously. By linear fits, the dn/dT curve exists two intersection points. The temperature range between two intersection points is regarded as Tcrosslinking. The crosslinking range of the polyurethane is determined as the range from 85°C to 122°C. It is examined and convinced by the measurement of electro-optic r33 coefficient of the poled polyurethane film with several temperatures in the range of Tcrosslinking at which poling is started.