Artificial Kerr effect on the self-focusing of laser in a dissipative suspension of metallic nanoparticles

Self-focusing of laser beam propagating through a dissipative suspension of metallic nanoparticles is studied. Impact of imaginary part of nanoparticle polarizability on the optical force and consequently on the particles rearrangement in the presence of laser fields with an initial Gaussian profile is considered. It is shown that considering absorption of wave, leads to the creation of optical force along the wave travelling direction which can cause longitudinal distribution of nanoparticles density. Considering fifth order nonlinearity of wave amplitude that comes from simultaneous considering of normal Kerr effect produced by the inhomogeneity of refractive index resulted from ponderomotive force acting on electrons and artificial Kerr nonlinearity caused by the polarization optical force acting on particles, set of differential equations describing nonlinear steady-state evolution of laser beam is derived by using a non-paraxial method. Evolution of laser spot size for different frequencies is investigated and optimum frequency range for improving focusing property is determined. It is shown that the artificial Kerr effect causes concentration of particles near the propagation axis that can reduce threshold power for occurring self-focusing.