Article

# Self-focusing and defocusing of twisted light in non-linear media.

Max Planck Institute of Microstructure Physics, Halle, Germany.

Optics Express (Impact Factor: 3.55). 12/2010; 18(26):27691-6. DOI: 10.1364/OE.18.027691 Source: PubMed

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**ABSTRACT:**We envisage the possibility of producing and tuning electronic orbital currents in atoms by weak, spatially inhomogeneous laser pulses with optical vortices. As already known, when interacting with such pulses an electronic system attains a definite amount of angular momentum. Here we explore this effect in the case when the system size is atomically small, i.e., much smaller than the scale of the inhomogeneity of the light pulses. We show that, nonetheless, angular momentum is transferred to the atomic system. The amount of the attained angular momentum depends on the position of the atom inside the field. Our numerical calculations and analytical analysis show that, indeed, light-induced orbital magnetism emerges in a dilute atomic gas when it is exposed to resonant or broadband optical vortices. This effect can be assessed, for instance, in a Faraday rotation experiment.Physical Review A 01/2012; 86:063812. · 3.04 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**In the present paper, we have proposed to exploit an analysis of a self-consistent, steady state, theoretical model, which explains the propagation of cosh-Gaussian laser beams in a plasma. The nonlinearity we have considered is of relativistic type. Using the expression for the dielectric function, we have setup the differential equation for beam-width parameter using the WKB and paraxial approximations. The effect of decentred parameter of the beam on the critical curve and the dependence of the beam-width on the distance of propagation have been specifically considered. The results have been presented in the form of graphs and discussed.Optics & Laser Technology 01/2012; 44:314-317. · 1.37 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**We predict a non-thermal magneto-optical effect for magnetic insulators subject to intense light carrying orbital angular momentum (OAM). Using a classical approach to second harmonic generation in non-linear media with specific symmetry properties we predict a significant nonlinear contribution to the local magnetic field triggered by light with OAM. The resulting magnetic field originates from the displacement of electrons driven by the electrical field (with amplitude $E_0$) of the spatially inhomogeneous optical pulse, modeled here as a Laguerre-Gaussian beam carrying OAM. In particular, the symmetry properties of the irradiated magnet allow for magnetic field responses which are second-order ($\sim E_0^2$) and fourth-order ($\sim E_0^4$) in electric-field strength and have opposite signs. For sufficiently high laser intensities, terms $\sim E_0^4$ dominate and generate magnetic field strengths which can be as large as several Tesla. Moreover, changing the OAM of the laser beam is shown to determine the direction of the total light-induced magnetic field, which is further utilized to study theoretically the non-thermal magnetization dynamics.Journal of optics 09/2014; 16(12). · 2.01 Impact Factor

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