• Surya P Tewari

      Articles written in Pramana – Journal of Physics

    • Picosecond optical nonlinearities in symmetrical and unsymmetrical phthalocyanines studied using the Z-scan technique

      S Venugopal Rao P T Anusha L Giribabu Surya P Tewari

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      We present our experimental results on the picosecond nonlinear optical (NLO) studies of symmetrical and unsymmetrical phthalocyanines, examined using the Z-scan technique. Both the open-aperture and closed-aperture Z-scan curves for three samples were recorded and the nonlinear coefficients were extracted from the theoretical fits. The nonlinear absorption/refraction contribution from the solvent was also identified. The observed open aperture behaviour for these molecules is understood in terms of the absorption coefficients of these molecules near 800 nm and the peak intensities used. It is established that these phthalocyanines exhibit large optical nonlinearities and, hence, are suitable for optical limiting applications.

    • Synthesis of Cu2O, CuCl, and Cu2OCl2 nanoparticles by ultrafast laser ablation of copper in liquid media

      Syed Hamad G Krishna Podagatlapalli Surya P Tewari S Venugopal Rao

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      Copper complex nanoparticles were fabricated from bulk copper using picosecond laser ablation in water and chloroform. We found that composition of the nanoparticles was CuCl and Cu2OCl2 in chloroform at three different input fluences; Cu2O in water which was confirmed from the data of EDAX, UV-Visible absorption spectra, and selected area electron diffraction pattern. We have also performed nonlinear optical studies of colloidal nanoparticles using Z-scan technique at 800 nm and ∼2 ps laser pulses. Cu2O NPs exhibited two-photon absorption at lower peak intensities while three-photon absorption was observed at higher peak intensities. Other samples exhibited two-photon absorption at all peak intensities.

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