Propagation of Surface Plasmons in Ordered and Disordered Chains of Metal Nanospheres

We report a numerical investigation of surface plasmon (SP) propagation in ordered and disordered linear chains of metal nanospheres. In our simulations, SPs are excited at one end of a chain by a near-field tip. We then find numerically the SP amplitude as a function of propagation distance. Two types of SPs are discovered. The first SP, which we call the ordinary or quasistatic, is mediated by short-range, near-field electromagnetic interaction in the chain. This excitation is strongly affected by Ohmic losses in the metal and by disorder in the chain. These two effects result in spatial decay of the quasistatic SP by means of absorptive and radiative losses, respectively. The second SP is mediated by longer range, far-field interaction of nanospheres. We refer to this SP as the extraordinary or non-quasistatic. The non-quasistatic SP can not be effectively excited by a near-field probe due to the small integral weight of the associated spectral line. Because of that, at small propagation distances, this SP is dominated by the quasistatic SP. However, the non-quasistatic SP is affected by Ohmic and radiative losses to a much smaller extent than the quasistatic one. Because of that, the non-quasistatic SP becomes dominant sufficiently far from the exciting tip and can propagate with little further losses of energy to remarkable distances. The unique physical properties of the non-quasistatic SP can be utilized in all-optical integrated photonic systems

The role of electron impact in the destruction of carbon monoxide molecules on the sun

Electron impact effect on solar C0 molecule destructio

Control in the spaces of ensembles of points

We study the controlled dynamics of the ensembles of points of a Riemannian manifold $M$. Parameterized ensemble of points of $M$ is the image of a continuous map $gamma:Theta o M$, where $Theta$ is a compact set of parameters. The dynamics of ensembles is defined by the action $gamma( heta) mapsto P_t(gamma( heta))$ of the semigroup of diffeomorphisms $P_t:M o M, t in mathbb{R}$, generated by the controlled equation $dot{x}=f(x,u(t))$ on $M$. Therefore, any control system on $M$ defines a control system on (generally infinite-dimensional) space $mathcal{E}_Theta(M)$ of the ensembles of points. We wish to establish criteria of controllability for such control systems. As in our previous work [A. Agrachev, Y. Baryshnikov, and A. Sarychev, ESAIM Control Optim. Calc. Var., 22 (2016), pp. 921--938], we seek to adapt the Lie-algebraic approach of geometric control theory to the infinite-dimensional setting. We study the case of finite ensembles and prove the genericity of the exact controllability property for them. We also find a sufficient approximate controllability criterion for continual ensembles and prove a result on motion planning in the space of flows on $M$. We discuss the relation of the obtained controllability criteria to various versions of the Rashevsky--Chow theorem for finite- and infinite-dimensional manifolds

Guiding, focusing, and sensing on the sub-wavelength scale using metallic wire arrays

We show that two-dimensional arrays of thin metallic wires can guide transverse electromagnetic (TEM) waves and focus them to the spatial dimensions much smaller that the vacuum wavelength. This guiding property is retained for the tapered wire bundles which can be used as multi-channel TEM endoscopes: they capture a detailed electromagnetic field profile created by deeply sub-wavelength features of the studied sample and magnify it for observation. The resulting imaging method is superior to the conventional scanning microscopy because of the parallel nature of the image acquisition by multiple metal wires. Possible applications include terahertz and mid-infrared endoscopy with nanoscale resolution.Comment: 3 figure

Rigidity of abnormal extrema in the problem of non-linear programming with mixed constraints

We study abnormal extremum in the problem of non-linear pro- gramming with mixed constraints. Abnormal extremum occurs when in necessary optimality conditions the Lagrange multiplier, which cor- responds to the objective function, vanishes. We demonstrate that in this case abnormal second-order su±cient optimality conditions guar- antee rigidity of the corresponding extremal point, which means iso- latedness of this point in the set determined by the constraints

Propogation of Surface Plasmons in Ordered and Disordered Chains of Metal Nanospheres

We report a numerical investigation of surface plasmon (SP) propagation in ordered and disordered linear chains of metal nanospheres. In our simulations, SPs are excited at one end of a chain by a near-field tip. We then find numerically the SP amplitude as a function of propagation distance. Two types of SPs are discovered. The first SP, which we call the ordinary or quasistatic, is mediated by short-range, near-field electromagnetic interaction in the chain. This excitation is strongly affected by Ohmic losses in the metal and by disorder in the chain. These two effects result in spatial decay of the quasistatic SP by means of absorptive and radiative losses, respectively. The second SP is mediated by longer range, far-field interaction of nanospheres. We refer to this SP as the extraordinary or nonquasistatic. The nonquasistatic SP cannot be effectively excited by a near-field probe due to the small integral weight of the associated spectral line. Because of that, at small propagation distances, this SP is dominated by the quasistatic SP. However, the nonquasistatic SP is affected by Ohmic and radiative losses to a much smaller extent than the quasistatic one. Because of that, the nonquasistatic SP becomes dominant sufficiently far from the exciting tip and can propagate with little further losses of energy to remarkable distances. The unique physical properties of the nonquasistatic SP can be utilized in all-optical integrated photonic systems