Abstract

The nonlinear properties of colloidal suspensions of dielectric nanoparticles (nanocolloids) were recognized since the 1980’s [1]. Nevertheless, this topic has attracted renewed interest in recent years due to the progress in the synthesis capabilities and applications of nanoparticles. In the case of dielectric nanoparticles, the colloidal medium exhibits a Kerr-like nonlinearity produced by the optical gradient force inducing a change in the concentration of particles owed to variations in the light intensity distribution. A gradient of the effective refractive index is generated in turn, which is responsible for a self-focusing effect. This is true regardless of the polarizability α of the particles, i.e., whether the refractive index of the particles is larger than that of the background (α>0) or in the opposite situation (α<0). Therefore, optical spatial solitons (OSS) can be generated in dielectric nanocolloidal suspensions [1, 2, 3]. Larger propagation distances were expected, in principle, in media with α<0 due to the depletion of scatterers from the beam path, giving rise to a self-transparency effect [2]. We have shown, however, that OSS with comparable propagation distances of several millimeters can be generated using dielectric nanocolloids with α>0 [3].

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