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The second order optical nonlinearity of zinc oxide thin films, grown on glass substrates by the dual ion beam sputtering technique under different deposition conditions are investigated. A relatively high nonlinear optical response, and evidence of dependence of the nonlinear coefficient on the deposition parameters is observed.

Charge injection and space charge effects were examined in electroluminescent polymer films through reflection electro-optical measurements. The approach was based on the standard electro-optic Teng and Man method, which allowed measurements of the values of the third-order response for the static Kerr effect. Only quadratic electro-optical effects were found due to the absence of polar groups and the centrosymmetric structure. The effects were associated with third-order optical nonlinearities.

Pulsed photo deflection in a modified collinear configuration was used to measure thermal diffusivity which was studied from the time evolution of the deflection signal. This method which is not applicable to these samples can be used to measure thermal diffusivity of a glass sample. The maximum time for which the probe beam deflects at a suitable distance from the pump beam is critical to this method.

Prism coupling of radiation inside a linear film over a nonlinear substrate is studied with a numerical method, showing that the change of coupling as a function of the input power in the case of a quasi-continuous operation (thermal nonlinearity) is influenced by a thermal gradient generated in the linear film. A comparison with experimental data confirms these calculations.

We successfully realized broad-band light-emitting color center waveguides buried in LiF crystals by using femtosecond laser pulses. The characterization of the waveguides was performed by optical microscopy, photoluminescence spectra, loss measurements and near-field profiling. The experimental results show that the direct-writing fabrication process induces low-index contrast active channel waveguides: their wavelength-dependent refractive index changes, estimated from 10-3 to 10-4 depending on the writing conditions, allow supporting few modes at visible and near-infrared wavelengths. [ABSTRACT FROM AUTHOR]

In this work we investigated the second-order nonlinear optical properties of a group of Disperse-Red-1-based electro-optic fluorinated copolymers, synthesized with two fluorinated monomers: the hexafluoroisopropyl alphafluoroacrylate monomer and the alphafluoroacrylate monomer bearing the Disperse Red 1 chromophore. Copolymers, with a concentration of chromophore substituted groups ranging from 46% to 75% molar, were synthesized and deposited as single films on glass substrates, for second-harmonic generation, and as sandwich structures with electrodes, for nonlinear ellipsometry measurements. For large concentrations of substituted groups, cracking of the films was observed and did not allow for any electro-optic characterization by nonlinear ellipsometry. The second-harmonic generation tensor main component d33 was retrieved by means of second-harmonic generation at λ=1064 nm for each concentration. The results obtained for the copolymer with the lowest concentration are compared with those obtained by nonlinear ellipsometry at λ=1550 nm and used as a calibration to infer information on the electro-optic properties at large concentrations. Stability of the poling-induced second-order nonlinear properties was checked by means of nonlinear ellipsometry. By using the temperature scanning technique, a depolarization temperature Tdep=124 °C was measured, while the use of the isothermal relaxation technique allowed to observe two different decay regimes, a Vogel-Fulcher-Taman-Hesse one for temperatures above 110 °C and an Arrhenius one for temperatures below 110 °C, with activation energy EA≈58 kcal/mol. [ABSTRACT FROM AUTHOR]

Polarization sensitive electroreflectance was used to study a typical hybrid photoconducting polymer–liquid crystal (LC) structure. Similar structures serve as optically addressed liquid crystalline spatial light modulators in real-time holography. It was shown that this technique might be used for the evaluation of internal electric-field changes in the vicinity of LC layer due to light-induced photogeneration and transport of charge carriers in the photoconducting polymer layer. A simplified theory presented in this work clarifies the experimental technique and the obtained results for the planar nematic LC panel. Employing the formalism of nonlinear optics for a particular type of LC (seven-component nematic mixture), we measured that the low-frequency (Ω/2π=1680 Hz) main component of a cubic optical susceptibility tensor χ[sub ijkl][sup (3)](-ω;0,Ω,ω) along the director direction is χ[sub a][sup (3)]=(7.4±1.5)×10[sup -16] m[sup 2]/V[sup 2]. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We used a single wavelength electro-optical reflection technique to study the creation of space charge distributions in a polymer light emitting diode, by monitoring the real third order nonlinear optical response of the electroluminescent layer. The diode is based on an aluminum/polymer/indium tin oxide stack, where the polymer is a derivative of poly(p-phenylene-vinylene) in which oxidiazole groups were grafted as side chains. The measured signal is strongly influenced by a space charge distribution and by screening in the organic layer. The space charge distribution is the superposition of a long lived contribution, close to indium tin oxide, due to charges trapped in deep levels, and of that of relatively mobile charges injected in the polymer film. In the frame of a model which takes into account Debye–Hu¨ckel screening, with screening length equal to 100 nm we estimated the carrier density of the long lived charge distribution to be 4.8×10[sup 23] m[sup -3], for a uniform distribution in a 110-nm-thick layer. The influence of the injection of mobile charges on the electro-optic signal is an order of magnitude smaller than that of trapped charges. The real third order susceptibility of the polymer is estimated to be χ[sup (3)]=4×10[sup -21] m[sup 2]/V[sup 2]. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]