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Author: search.filters.author.Rao, A.Subject: search.filters.subject.Optical films

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    Influence of annealing on the linear and nonlinear optical properties of Mn doped ZnO thin films examined by z-scan technique in CW regime
    (Elsevier B.V., 2016) Nagaraja, K.K.; Pramodini, S.; Poornesh, P.; Rao, A.; Nagaraja, H.S.
    We present the studies on the influence of annealing on the third-order nonlinear optical properties of RF magnetron sputtered manganese doped zinc oxide (MZO) thin films with different doping concentration. It is revealed that the incorporation of Mn into ZnO and annealing lead to prominent changes in the third order nonlinearity. Nonlinear optical measurements were carried out by employing the z-scan technique using a continuous wave (CW) He-Ne laser of 633 nm. The z-scan results reveal that the films exhibit self-defocusing thermal nonlinearity. The third-order nonlinear optical susceptibility ?(3) was found to be of the order of 10-3 esu and 10-2 esu for annealed MZO thin films at 200 °C and 400 °C respectively. The dependence of grain size on the observed nonlinearity was revealed by atomic force microscopy analysis. Optical limiting studies were carried out for a range of input power levels and an optical limiting of about ?8 mW was observed indicating the possible application for photonic devices. © 2016 Elsevier B.V. All rights reserved.
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    A systematic investigation on structural, electrical, linear and nonlinear optical properties of Zn:CdO thin films for optoelectronic applications
    (Elsevier B.V., 2021) Nagaraja, B.S.; Gurumurthy, S.C.; Bairy, R.; Koduri, K.; K, B.; Rao, A.
    In the present work, a systematic study on structural, electrical, linear, and nonlinear optical properties of Zn doped CdO thin films prepared by Spray Pyrolysis (SP) technique is reported. X-ray diffraction (XRD) studies revealed the cubic, wurtzite structure, and polycrystalline nature of all the films. The observed results showed a decrease in lattice constant and unit cell volume with an increase in Zn doping concentration. Morphology study confirms uniform distribution of spherical grain-like structure with small voids. An increase in direct and indirect bandgap is observed with doping concentration up to 5 wt%, and the trend reverses at higher concentration. The significant effect of Zn doping on optical parameters such as absorption coefficient, extension coefficient, refractive index, optical dielectric constant, and optical conductivities are calculated for all thin films. Further, the optical studies were used to analyze the linear susceptibility, third-order nonlinear optical susceptibility, and nonlinear refractive index of the films. The observed values for ?(1),?(3) and n2 are in the range from 0.03 to 0.09 esu, 3.51×10?16 to 1.02×10?14 esu, and 1.09×10?14 to 2.67×10?13 esu for pure and Zn doped thin films respectively. Hall coefficient and electrical studies indicate that the Zn doping influences the electrical properties. An n-type and ohmic behavior is also observed for these films. Optical and electrical results suggest that these Zn:CdO films can be a potential candidate for optoelectronic applications. © 2021 Elsevier B.V.