Nagaraja, K.K.Pramodini, S.Poornesh, P.Nagaraja, H.S.2026-02-052013Journal of Physics D: Applied Physics, 2013, 46, 5, pp. -223727https://doi.org/10.1088/0022-3727/46/5/055106https://idr.nitk.ac.in/handle/123456789/26829We report on the studies of the effects of annealing on the structural and third-order nonlinear optical properties of ZnO thin films deposited on quartz substrates by the RF magnetron sputtering technique. The films were annealed in the temperature range 400-1000 °C. The third-order nonlinear optical studies were carried out using the z-scan technique under continuous wave (cw) He-Ne laser irradiation at 633 nm wavelength. The effects of annealing on the structural properties were examined using x-ray diffraction and atomic force microscopy (AFM). The (0 0 2) preferred orientation increased with increase in annealing temperature up to 800 °C. The crystalline phases of SiO2 were observed at higher annealing temperatures. The appearance of an extraneous phase was confirmed by AFM images and optical transmittance spectra. The samples exhibited nonlinear absorption and nonlinear refraction under the experimental conditions. The negative sign of the nonlinear refractive index n2 indicated that the films exhibit self-defocusing property due to thermal nonlinearity. The nonlinear refractive index n2, the nonlinear absorption coefficient ?eff and the third-order optical susceptibility ?(3) were found to be of the highest orders. The estimated value of third-order optical susceptibility ?(3) was of the order of 10-3 esu. Multiple diffraction rings were observed when the samples were exposed to the laser beam. The appearance of rings was due to the refractive index change and thermal lensing. With increase in laser intensity, the variations of the self-diffraction ring patterns were studied experimentally. The films also exhibited strong optical limiting properties under cw laser excitation, and reverse saturable absorption was the dominant process leading to the observed nonlinear behaviour. © 2013 IOP Publishing Ltd.AFM imageAnnealing temperaturesContinuous wavesCrystalline phasisDominant processExperimental conditionsHe-Ne laser irradiationLaser intensitiesMultiple diffractionNon-linear optical propertiesNon-linear refractionNonlinear absorption coefficientNonlinear absorptionsNonlinear behavioursNonlinear optical studiesNonlinear refractive index n2Optical limiting propertiesOptical transmittance spectrumPreferred orientationsQuartz substrateRefractive index changesReverse saturable absorptionRF magnetron sputtering techniqueRing patternsSelf-defocusingSelf-diffractionTemperature rangeThermal lensingThermal nonlinearitiesThird order nonlinear optical propertiesThird order optical susceptibilityThird-orderZ-scan techniqueZnO thin filmAnnealingAtomic force microscopyContinuous wave lasersLaser excitationMagnetron sputteringMetallic filmsOptical filmsQuartzRefractive indexSemiconductor quantum wellsX ray diffractionNonlinear optics