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The crucial role of nonlinear propagation effects in the self-guiding of femtosecond laser pulses required accurate representation of nonlinearities to describe them. In this paper, an improved theoretical model has been proposed to study the height distribution of the atmospheric nonlinear refractive index. The results show that the revised model obviously improves accurate estimation of nonlinear index at the long wavelength band. Based on the model, we also found the atmospheric nonlinear refractive index differs much from the lower atmosphere to the upper atmosphere. Our results are essential for engineering applications based on the long-distance ultrashort laser pulses' transmission in diverse atmosphere. [ABSTRACT FROM AUTHOR]

We investigate the effect of entering metallic core-shell nanoparticles in Silica glass to increase its nonlinear susceptibility (NLS). Third-order NLS and figure of merit ( FOM) relations of this composite are driven with the T-Matrix method. Effect of nanoparticle volume fraction, shell-to-core radius ratio and core, clad and host material in the real and imaginary part of these parameters are studied. It is concluded that doping Silica with Copper core-Gold clad nanoparticles make the compound FOM-enhanced. [ABSTRACT FROM AUTHOR]

We have synthesized highly stable silver nanoparticles in aqueous solution at room temperature by standard reduction method using bovine serum albumin (BSA) as a stabilizing agent. The nonlinear optical properties of nanoparticles were investigated using Z-scan technique at 532 nm. The obtained nonlinear absorption coefficient and negative nonlinear refractive index is found to be 88.36 cm/GW and -5.1 × 10-7 esu respectively. The real and imaginary part of third order susceptibility of silver nanoparticles is found to be 1.553 × 10-7 esu and 0.7 × 10-7 esu respectively. The silver nanoparticles in BSA template show good optical limiting property. [ABSTRACT FROM AUTHOR]

The linear and nonlinear response of a four-level EIT system driven by three coherent fields is investigated. It is found that at appropriate atomic parameters, the Kerr nonlinearity can clearly be enhanced. It is also demonstrated that the maximal Kerr nonlinearity enters the EIT window, and the corresponding linear and nonlinear absorption suppress. Moreover, we show that nonlinear absorption and Kerr nonlinearity can also be changed via relative phase between driving fields. [ABSTRACT FROM AUTHOR]

The nonlinear susceptibility of atoms interacting with an intense laser field has been investigated using numerical solution of the time-dependent Schrödinger equation. It was found that the behavior of nonlinear susceptibility strongly depends on the intensity; it increases linearly in low intensity regime (Kerr nonlinearity), then saturates at higher intensity. Furthermore, it has also been found that the nonlinear susceptibility is substantially influenced by the onset of ionization. [ABSTRACT FROM AUTHOR]