Z. Sofiani

Third harmonic generation in undoped and X doped ZnO films (X: Ce, F, Er, Al, Sn) deposited by spray pyrolysis

There is a current interest in research of wide band gap semiconductor materials for the purposes of third order nonlinear optical properties in view of optoelectronics applications. Materials for nonlinear optics should present important changes of nonlinear intensity, dependence on changes of nonlinear refractive index, short response time, and weak absorption losses. We report the results of the third order nonlinear optical susceptibilities of undoped and doped (cerium, fluorine, erbium, aluminum, and tin) zinc oxide films using the third harmonic generation technique at 1064 nm wavelength region in picoseconds regime. Thin films were grown on glass substrate by the spray pyrolysis technique at different temperatures of substrates and characterized by using the x-ray diffraction, scanning electron microscope, transmission, and photoluminescence. A strong third harmonic signal was obtained from the studied films with a good crystallinity and roughness. We have found that at high conductivity, there is ...

Second and third order nonlinear optical properties of microrod ZnO films deposited on sapphire substrates by thermal oxidation of metallic zinc

We report the preparation of microcrystalline ZnO thin films on sapphire substrates using a simple method based on the thermal evaporation of metallic Zn in vacuum with further annealing process. The aim of annealing in the oxygen atmosphere in the range of 800–850°C was to obtain the high quality ZnO films. The surface morphology was studied by scanning electron microscopy and atomic force microscopy. The polycrystalline films with ZnO microrods at different stages of their growth were investigated. Second and third harmonic generation measurements were performed by means of the rotational Maker fringe technique using Nd:YAG laser at 1064nm in picosecond regime. The obtained values of second and third order nonlinear susceptibilities were found to be high enough for the potential applications of the investigated materials in the optical switching devices based on refractive index changes.We report the preparation of microcrystalline ZnO thin films on sapphire substrates using a simple method based on the thermal evaporation of metallic Zn in vacuum with further annealing process. The aim of annealing in the oxygen atmosphere in the range of 800–850°C was to obtain the high quality ZnO films. The surface morphology was studied by scanning electron microscopy and atomic force microscopy. The polycrystalline films with ZnO microrods at different stages of their growth were investigated. Second and third harmonic generation measurements were performed by means of the rotational Maker fringe technique using Nd:YAG laser at 1064nm in picosecond regime. The obtained values of second and third order nonlinear susceptibilities were found to be high enough for the potential applications of the investigated materials in the optical switching devices based on refractive index changes.

Influence of Roughness Surfaces on Third-Order Nonlinear-Optical Properties of Erbium-Doped Zinc Oxide Thin Films

ABSTRACT Zinc oxide (ZnO) and erbium-doped zinc oxide (ZnO:Er) thin films were deposited on heated glass substrates using the spray pyrolysis technique. Third-order nonlinear-optical properties of the thin films have been investigated using the third harmonic generation (THG) at wavelength of 1064 nm in picosecond regime. The dependence of third-order nonlinear susceptibility and transmission characteristics on the thin films roughness has been evaluated. Third-order nonlinear optical susceptibility (χ(3)) values of the studied materials were in the remarkable range of 10−2 esu. The morphologic properties of the deposited films have been analyzed using x-ray diffraction (XRD) and atomic force microscopy (AFM) and the luminescence properties by cathodoluminescence (CL). A correlation between optical properties and structural properties is given.

Third-order nonlinear optical properties of CuPc: influence of thickness and concentration

The concentration dependence of third order nonlinear optical susceptibility ( χ<3> ) of copper phthalocyanine (CuPc) dissolved in tetrahydrofuran (THF) using the degenerate four wave mixing (DFWM) method at 532 nm was investigated. We present the linear dependence of the third order nonlinear optical susceptibility ( χ<3> ) as a function of different concentration for CuPc dissolved in THF. We also calculated the second order hyperpolarizability ( γ) of CuPc solutions. Third harmonic generation (THG) measurements at the 1064 nm performed on CuPc thin films are also presented. We found that the χ<3>DFWM values are larger than the χ<3>THG ones. This variation observed in χ<3> values, occurs probably due to the different resonance contributions in solution and solid state of CuPc. We show that in the case of DFWM measurements the one and two-photon resonant contributions at the Q and C-band increase χ<3>DFWM value of CuPc. In THG measurements, the three-photon resonance contribution at the Soret band gives rise to higher χ<3>THG value.

Grown of ZnO:Ce layers by spray pyrolysis method for nonlinear optical studies

We have investigated the linear and nonlinear optical properties of high quality cerium-doped zinc oxide films (ZnO:Ce). The layers were grown by the reactive chemical pulverization spray pyrolysis technique using zinc and cerium chlorides as precursors at temperature up to 450/spl deg/C. The influence of Ce concentration on the structural, linear and nonlinear optical properties of ZnO thin films is presented. The films were characterized by X-ray diffraction, scanning electron microscope and photoluminescence measurements. The X-ray diffraction analysis indicates that all films are polycrystalline in nature and clearly shows the appropriate incorporation of the Ce atoms in the ZnO films. The third order nonlinear optical properties, which are the main subject of this investigation, were studied. For this propose, the third harmonic degeneration (THG) technique has been employed. A laser source has been used for the fundamental beam at 1064 nm so that the generated third harmonic signal is made at 355 nm.

Cathodoluminescence Properties of Zno Thin Films

The industry has a great need for high performance materials to feature well defined. These needs have prompted the development of methods of study and control of gradually more sophisticated based on the radiation-matter interaction. To identify the properties of materials, we must make a spectral analysis on the emitted photon using a spectrometer combined with a detection system. The analysis of the photon can take place directly in the form of an electrical current, as well as the spectrum received by the measurement system is represented by a function I (λ).

Structural, optical and photoluminescence properties of Al doped ZnO thin films by spray pyrolysis

Undoped and aluminium doped zinc oxide thin films were deposited by the spray pyrolysis technique onto the glass substrates at 450°C using a precursor solution consisting of zinc chloride (AlCl3). The structural, optical and photoluminescence properties of these films were investigated as a function of Al concentration (0, 3, 5, 7 and 10 at %). The films showed a hexagonal wurtzite structure and high preferential orientation in the (0 0 2) crystallographic direction. The optical transmittance spectra showed transmittance higher than 80% in the visible region. The Al doping has improved the crystallinity and the luminescence in the visible region.

Effect of substrate temperature on the stress and blue light emission of nanostructured In2O3-F thin films prepared by spray pyrolysis

Nanocrystalline Fluorine-doped indium oxide (IFO) thin films have been deposited with various substrate temperatures by reactive chemical pulverization spray pyrolysis technique onto glass substrates. The effect of substrate temperature (Ts) on the stress and luminescence properties was investigated in detail using X-ray diffraction, transmission, photoluminescence spectroscopy, electrical resistivity and scanning electron microscopy (SEM). XRD analysis confirmed the cubic structure of polycrystalline In2O3. The preferred growth orientation along (222) plane shifts to (400) and the compressive stress decreases from 1.20 to 0.11 GPa when the substrate temperature was increased from 400 to 500 °C. The photoluminescence (PL) spectra of (IFO) present two blue and a yellow emission. Intensive blue PL bands at 414 and 436 nm were observed in the samples deposited at 500°C, which present the strongest orientation along (400) peak and a lower resistivity of 1.4 × 10-2 Q cm. A shift of blue peaks to shorter wavelength of (IFO) films has also been observed with the increase of Ts and this may be attributed to the change of stress present in the films.

Theoretical calculations of second and third-order nonlinear susceptibilities and their corresponding hyperpolarizabilities of a styrylquinolinium dye

The second (Xexp(2)) and third-order (Xexp(3)) susceptibilities of a styrylquinolinium dye (1) have been determined utilizing second-harmonic generation (SHG) and third-harmonic generation (THG) techniques, respectively. The reported measurement findings on Xexp(2) and Xexp(3) have been compared with the theoretical data evaluated here by means of ab-initio quantum mechanical calculations. The electric dipole moments (μ), static dipole polarizabilities (a) and first hyperpolarizabilities (β) have been computed by density functional theory (DFT) at B3LYP/6-311+G(d, p) level. To reveal the frequency-dependent second and third-order microscopic nonlinear optical (NLO) behavior of the title compound, the dynamic dipole polarizabilities, first and second (γ) hyperpolarizabilities have been theoretically investigated using time-dependent Hartree-Fock (TDHF) method. According to the experimental and theoretical results, the values of susceptibilities and the corresponding microscopic coefficients with large non-zero responses make the examined dye promising candidate for NLO applications.

The lithium effect on the blue and red emissions of Er-doped zinc oxide thin films

Lithium- and erbium-codoped zinc oxide thin films have been successfully deposited on heated glass substrates using the spray pyrolysis technique. This study is an investigation of the Li effect on the enhancement of cathodoluminescent intensity on Er-monodoped ZnO films. Crystallinity, morphology and luminescence characteristics were investigated in detail by x-ray diffraction, scanning electron microscopy and cathodoluminescence. The Li‐Er-codoped ZnO films show a higher intensity of blue and red emissions than the Er-monodoped ZnO films. The behaviour of that enhancement is attributed to the modification of the local symmetry of the Er 3+ ion, which increases the intra 4f transition of the Er 3+ ion. The blue and red emissions have an important effect to improve the capacity of data storage.