Teng-Man Technique Research Articles

Strain engineering of the electro-optic effect in polycrystalline BiFeO3 films [Invited

Electro-optic thin film materials, which change their refractive index upon the application of an electric field, are crucial for the fabrication of optical modulators in integrated photonic circuits. Therefore, it is key to develop strategies to tune the linear electro-optic effect. Strain engineering has arisen as a powerful tool to optimize the electro-optic coefficients in ferroelectric thin films. In this report, the electro-optical properties of polycrystalline bismuth ferrite (BiFeO3) thin films are studied. The electro-optic coefficients (reff) of low-cost solution-processed BiFeO3 films under different substrate-induced thermal stress are characterized using a modified Teng-Man technique in transmission geometry. The influence of poling state and substrate stress on the electro-optical properties are discussed. The films show a notable piezo-electro-optic effect: the effective electro-optic coefficient increases both under compressive and tensile in-plane stress, with compressive stress having a much more profound impact. Electro-optic coefficients of 2.2 pm/V are obtained in films under a biaxial compressive stress of 0.54 GPa.

Planar Phase Electro-Optical Modulator Based on Chromophore-Doped Polyimides

Experimental studies of nonlinear optical and electro-optical properties of original synthesized chromophore-doped polyimides with a covalently attached DR-13 dye are reported. Second harmonic generation measurements are compared with the results of direct electro-optical response measurements by the Teng–Man technique. High temperature stability of the examined polyimides is observed. Methods of creating a planar phase electro-optical modulator with the use of synthesized chromophore-doped polyimides are designed and elaborated. The optical and electro-optical characteristics of the modulator are presented.

Mechanism that governs the electro-optic response of second-order nonlinear polymers on silicon substrates

We use a modified Teng-Man technique to investigate the poling induced electro-optic activity of chromophore-doped organic polymers poled on silicon substrate in a thin film sample configuration. We reveal a fundamental difference between the poling processes on silicon substrate and ITO substrate. The electro-optic activity for polymers poled on silicon substrate is reduced which we ascribe to space charge formation at the silicon - organic interface that distorts the field distribution in the polymer film during high field poling, and therefore limits the effective induced polar order. We demonstrate that the electro-optic activity on silicon substrate can be improved by inserting a 5 nm thin dielectric layer of Al2O3 between the silicon substrate and the polymer which reduces the leak-through current during poling, thereby allowing for higher applicable poling voltages.

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.

Modification of a Teng-Man technique to measure both r33 and r13 electro-optic coefficients

In this paper, we present a modified Teng-Man method to measure both electro-optic coefficients in a single measurement. Using our method, we confirm a linear dependence between the applied poling field and the measured electro-optic coefficients. The ratio between the two electro-optic coefficients is close to three, which is theoretically expected from a weakly oriented polymer film. Since conductive silicon is used as substrate, no auxiliary layers of transparent oxide or metal are required on the substrate, which simplifies both the sample preparation and the evaluation of the results.

Synthesis of novel two-dimensional spindle-type fluorinated nonlinear optical chromophores

Two novel two-dimensional spindle-type fluorinated chromophores with fluorinated phenyl as side groups connecting to the π conjugated bridge were prepared for second-order nonlinear optical applications. The detailed synthetic procedure was reported. Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) revealed that the spindle-type fluorinated chromophores have excellent thermal stability. Host–guest doped materials had been used to prepare the second-order nonlinear optical films. The nonlinear electro-optic (EO) coefficient of the poled films was measured by Teng–Man technique at the fundamental wavelength of 1310 nm, and the r 33 up to 28 pm/V was achieved.

The preparation of two-dimensional spindle-type chromophores for second-order nonlinear optical materials

A series of two-dimensional spindle-type chromophores has been synthesized. The detailed synthetic procedure was reported. The factors that influence the nonlinear optical properties such as the donors and acceptor character have been investigated. The chemical structures of the target products have been confirmed by IR, UV–Vis and NMR spectroscopy, elemental and thermal analysis. The spindle-type chromophores have been used to prepare host-guest doped films which exhibited very good thermal and temporal stability. The nonlinear electro-optical coefficients of the host-guest doped films were measured by the Teng-Man technique and gave values in the range from 21 to 29 pm/V.

Novel photo-cross-linkable polymer bearing spindle-type chromophores for second-order non-linear optical materials

A new strategy to tackle the orientation-relaxation of the chromophores was developed and used to prepare a film which was consisted of polymethyl methacrylate (PMMA) and photo-cross-linkable polyurethane oligomer (PU). The PU contained spindle-type chromophore and terminated with methacrylolyl groups as cross-linkable group. The chemical reaction process was characterized by infrared spectroscopy and the structure of reaction products were characterized by NMR spectroscopy. The surface morphology of the films was investigated by atomic force microscopy (AFM) images. The electro-optic (EO) coefficient of the prepared film was measured by using Teng-Man technique. The cross-linked films containing 15 wt% of the chromophore units displayed a high EO coefficient up to 41 pm/V. The 5% weight loss temperature was 228 °C for the film after photo-cross-linking. Compared with the uncross-linked films, their thermal and temporal stability were greatly improved.

Design, Synthesis, and Characterization of Crosslinkable Doped NLO Materials Based on Polyurethanes Containing Spindle‐Type Chromophores

AbstractSpindle‐type chromophore molecules have been successfully designed and synthesized. Furthermore, a new series of main‐chain second‐order nonlinear PUs with spindle‐type chromophore molecules have been prepared. These PU offered good processability; thus thin films of optical‐quality could be easily prepared from their solutions. The molecular structural characterization of the resulting PU was achieved by 1H NMR and FTIR spectroscopy and elemental analysis. TGA measurement of the PU showed that they had good thermal stability with decomposition temperature higher than 250 °C. The nonlinear electro‐optic coefficient of the PU‐2/poly(MMA‐co‐GMA) doped film was measured up to 32 pm · V−1 by Teng‐Man technique after poling and crosslinking. magnified image

Prepare organic/inorganic hybrid nonlinear optical material containing two-dimensional spindle-type chromophores

In this paper, functionalized alkoxysilane dye (ICTES-STC) was formed by the reaction of two-dimensional spindle-type chromophores (STC) with 3-isocyanatopropyltriethoxysilane (ICTES). The transparent films having silica network matrix and covalently bonded chromophores were fabricated via the sol–gel process. From TGA thermogram, the initial decomposition temperature of the hybrid film was determined to be 269 °C. The electro-optic (EO) coefficient (r 33) of the poled films was measured to be around 12 pm/V by Teng–Man technique. The thermal stability of the NLO coefficient of the film was investigated by the depoling experiment and temporal decay test, and the result showed that the hybrid film had a good thermal stability, implying its potential applications for EO devices.

Comparison of r_33 values for AJ404 films prepared with parallel plate and corona poling

We report on the measured electro-optic coefficients of approximately 150 pm/V at 1310 nm and 1550 nm for poled guest-host polymer films made with the chromophore AJ404L. Films were poled using corona poling and parallel-plate poling techniques. The films were fabricated and poled and the electro-optic coefficients measured by two independent laboratories. Corona-poled AJ404L films were spun onto indium-tin oxide-coated glass substrates with and without a cladding layer of UV15LV. The r33 value for the films were measured using the Teng-Man technique for both corona-poled and parallel-plate poled films.

Precision Teng-Man Electro-Optic Measurements Using Highly Near-Infrared Transparent Electrodes

AbstractA series of highly near-infrared (NIR) transparent In2O3 thin films has been grown by ion-assisted deposition (IAD) at room temperature, and their optical and electrical properties characterized. The NIR transparency and the plasma edge can be engineered through control of the film deposition conditions. The as-deposited In2O3 thin films were employed as transparent electrodes for direct electro-optic (EO) characterization measurements via the Teng-Man technique. Using LiNbO3 as the standard, the relationship between the degree of electrode NIR transparency and Teng-Man EO measurement accuracy was evaluated. It is found that In2O3 electrodes can be tailored to be highly NIR transparent, thus providing more accurate Teng-Man EO coefficient quantification than ITO (tin-doped indium oxide). In addition, the EO coefficients of stilbazolium-based self-assembled superlattice (SAS) thin films were directly determined for the first time by the Teng-Man technique using an optimized In2O3 electrode. EO coefficients r33 of 42.2, 13.1, and 6.4 pm/V are obtained at 633, 1064, and 1310 nm, respectively.

Near-infrared transparent electrodes for precision Teng–Man electro-optic measurements: In2O3 thin-film electrodes with tunable near-infrared transparency

Highly near-infrared (NIR) transparent In2O3 thin films have been grown by ion-assisted deposition at room temperature, and the optical and electrical properties characterized. NIR transparency and the plasma edge frequency can be engineered by control of the film deposition conditions. As-deposited In2O3 thin films were employed as transparent electrodes for direct thin film electro-optic (EO) characterization measurements via the Teng–Man technique. Using LiNbO3 as the standard, the relationship between electrode NIR transparency and Teng–Man EO measurement accuracy was evaluated. It is found that In2O3 electrodes can be tailored to be highly NIR transparent, thus providing far more accurate Teng–Man EO coefficient quantification than tin-doped indium oxide. In addition, the EO coefficients of stilbazolium-based self-assembled superlattice thin films were directly determined for the first time using an optimized In2O3 electrode. EO coefficients r33 of 42.2, 13.1, and 6.4pm∕V are obtained at 633, 1064, and 1310 nm, respectively.

On the measurement of the electro-optic properties of poled side-chain copolymer films with a modified Teng–Man technique

We report on the measurement of the electro-optic properties of poled side-chain copolymer films by means of a time-resolved ellipsometric version of the Teng and Man experiment. The polymer is a side-chain Disperse Red 1 substituted poly(methyl methacrylate). The technique makes use of polymer layers sandwiched between indium tin oxide and metal electrodes. We show that the technique can give a good evaluation of the real electro-optic properties if operated in a wavelength range outside the absorption bands of the indium tin oxide layers. In this case we evaluated the temperature dependence of the relaxation time constant and found that it is described by an Arrhenius like dependence as a function of temperature. The activation energies and the time constants are in agreement with data reported in literature.