PhD Theses (Physics)

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Browsing PhD Theses (Physics) by Author "Behera, Sasmita"

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    Influence of Cu Nano-Layer on Nonlinear Optical Response of BTO, STO and BST Thin Films Fabricated via Pulsed Laser Deposition
    (2022) Behera, Sasmita
    The present thesis was focused on the fabrication and characterization of perovskite thin films of BaTiO3, SrTiO3, Ba1-xSrxTiO3 (0 ≤ x ≤ 1) via pulsed laser deposition (PLD) technique. The optimized substrate temperature and background oxygen pressure were found to be 700 °C and 0.1 mbar, respectively. The morphology, structural, linear, and nonlinear optical properties of all thin films were studied by AFM and FESEM, XRD, Raman, UV-Visible-NIR spectroscopy, and modified Z-scan technique. The values of nonlinear absorption coefficient (β) for BaTiO3, SrTiO3, and Ba0.5Sr0.5TiO3 thin films fabricated at optimized conditions were found to be (57.54 ± 0.05), (63.51 ± 0.13), (73.24 ± 0.32) cm/W, respectively. It has already been known that the NLO properties can be further enhanced by embedding with metallic nanoparticles. Therefore, the effect of Cu nano-layer on structural, linear, and nonlinear optical properties of host matrix of BaTiO3, SrTiO3, and Ba0.5Sr0.5TiO3 thin films have been studied and observed that the sequence of Cu nano-layer is important for SPR and enhancement in NLO properties. The nonlinear absorption coefficients (β) of Cu infused BaTiO3, SrTiO3, and Ba0.5Sr0.5TiO3 thin films were found to be (155.04 ± 5.39), (182.34 ± 7.23) and (188 ± 0.45) cm/W, respectively. The values of the third-order nonlinear optical coefficients (β, n2, and χ (3)) in Ba1-xSrxTiO3 (0 ≤ x ≤ 1) thin films were found to be in the range of (64.74 – 74.85) cm/W, (0.18– 6.35) ×10-3 cm2/W and (12.43-63.11) × 10-4 esu, respectively. The optical limiting response of BaTiO3, SrTiO3, and Ba0.5Sr0.5TiO3 thin films deposited on quartz and MgO substrates was analysed and measured the optical limiting threshold as well. The obtained high third-order nonlinearity and low optical limiting threshold in present films are promising for optoelectronics and photonics devices and can be used as optical limiters and optical switching applications.