Fluctuating isotropic electromagnetic fields are obtained by considering a large group of plane waves with wave vectors, polarizations and phases randomly distributed and fluctuating on time. Due to the isotropic character of this electromagnetic field, the optical force induced on an electric dipole is, in average, equal to zero. However, the dynamics of electric dipoles on these kind of systems are far from being trivial. In this work we analyze the dynamics of two dipoles using molecular dynamics simulations. In particular, we consider two silver nanoparticles of 5nm radius at Fr¨ohlich resonance. Under these conditions a gravity-like interaction among the two particles is induced. The molecular dynamics numerical simulations show how Keplerian-like trajectories are obtained under these particular conditions
Scattering forces on small particles are proportional to the average value of the Poynting vector and to the curl of the spin angular momentum of the light field. In this paper we analyse the relevance of spin non-conservative forces in configurations where scattering forces are different from zero with a null Poynting vector or with a null average value of the Poynting vector.
The coherent combination of electric and magnetic responses is the basis of the electromagnetic behavior of new engineered metamaterials. The basic constituents of their meta-atoms usually have metallic character and consequently high absorption losses. Based on standard "Mie" scattering theory, we found that there is a wide window in the near-infrared (wavelengths 1 to 3 μm), where light scattering by lossless submicrometer Ge spherical particles is fully described by their induced electric and magnetic dipoles. The interference between electric and magnetic dipolar fields is shown to lead to anisotropic angular distributions of scattered intensity, including zero backward and almost zero forward scattered intensities at specific wavelengths, which until recently was theoretically established only for hypothetically postulated magnetodielectric spheres. Although the scattering cross section at zero backward or forward scattering is exactly the same, radiation pressure forces are a factor of 3 higher in the zero forward condition.
Intense optical fields can induce significant forces "between"
particles. In analogy with atomic physics, the resonant modes of a
single particle play the role of electronic orbitals and, like
their electronic counterparts, could lead to bonding and
antibonding interactions between neighboring particles. In absence
of absorbing or "Mie"-like resonances, light forces on small
particles are, in general, very small. However, as we will show,
when the fields are confined in quasi-one-dimensional waveguide
structures, the coupling of the scalar dipolar field with the
waveguide modes leads to a resonant total reflection close to the
threshold of a new propagating mode. These resonant modes are
shown to lead to unusual strong optical interactions between
Colloidal liquids usually appear turbid due to the strong multiple scattering of electromagnetic waves from the particles in suspension. As the concentration increases, particle interactions induce positional correlations which generally lead to a reduced optical density (higher transparency). However, the optical properties of a colloidal liquid can be manipulated by tuning the interaction potential between particles. In the presence of repulsive interactions, colloidal liquids show fascinating photonic properties despite their overall disorder. Short range structural order enhances the scattering strength at certain configurations while at the same time the total light transmission shows strong wavelength dependence, reminiscent of photonic crystals. The tunable optical properties of these photonic liquids suggest potential applications such as transparency switches or improved sunblockers. On the other hand the interplay between order and disorder and the scattering properties of these systems are strikingly similar to those discussed in the transport of electrons in liquid metals. Close to the Bragg condition the transport cross section becomes anisotropic and the transmission coefficient is reduced. In materials with high refractive index mismatch such an effect might open an alternative pathway to localization of light.
The conductance of nano-sized, surface disordered wires is theoretically analyzed all the way during an elongation process. Even though wire cross-section is kept constant during the whole process, the statistical analysis of the conductance reveals clear preference to take values close to integer multiples of the conductance quantum. We show that this is a consequence of having a very small number of channels and surface disorder only.