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We have studied the influence of the structural disorder on the spatial distribution of the plasmonic field and its propagation in one and two dimensional arrays of coupled metallic nanowires. By solving the three dimensional Maxwell equations we have studied the Anderson localization of surface Plasmon polaritions for arrays of metallic nanowires with varying degree of the structural disorder. We have found that a random distribution of radii of the nanowires leaded to transverse spatial localization of collective surface plasmonic polarition excitations. The characteristic spatial confinement of the plasmonic field found smaller than the optical wavelength which demonstrated that plasmonic structures can be employed to implement the subwave length Anderson localization of the electromagnetic field. We have also found that influence of the metallic loss and the gain of the host medium on the plasmonic Anderson localization modes, loss was compensated by the gain whose strength was much smaller than the loss rate of the metallic component of the plasmonic array. The obtained results were found in good agreement with previously obtained results. [ABSTRACT FROM AUTHOR]

We have studied a mathematical framework of higher-order multipole fields in the vicinity of optical nanoantennas. We have exemplified at suitably chosen Nanoantennas i.e. a Nano antenna which strongly enhances the quadruple field. The modification of excitation rates in quantum mechanical systems due to this quadrupolar enhancement was studied. The hybrid system consisting of an optical Nano antenna and a quantum mechanical three level system was studied in detail. A properly designed Nano-antenna can excite dipole for bidden transitions in three level systems due to the enhanced higher order multipole fields. The dynamics of the system is strongly altered by the presence of the nanoantenna and cannot be done by the quadrupolar enhancement alone. This can be achieved by enhancing higher order multipole fields near the antenna. A quadrupole transition as the dominant excitation channel in a three level system was considered. It was found that the enhancement of this transition significantly intensify subsequent emission processes with respect to altered emission characteristics. The effects depend on geometrical parameters; the properties of the optical nanoantenna can be tailored and hence allowed for direct implementations in spectroscopies schemes. The obtained results were found in good agreement with previously obtained results. [ABSTRACT FROM AUTHOR]

We have studied the resonant properties of circular optical nanoantennas as well as other shapes of optical antennas without requiring any fitting parameters. This allows for a deeper insight into scaling behavior and do faster further research since a desired simple tool is now available to design such nanoantennas. The theory has been applied to design antennas supporting various resonances at predefined frequencies to respond to the desire to have multi resonant antennas for applications. Raman sensors are extremely broad band resonators. Such circular patch nanoantennas consist in tailoring the dispersion relation and the complex reflection coefficient at will by carefully selecting a particular stack of layers. We have made to characterize the resonance behavior of the potentially simplest optical nanoantennas which is also called nanowire antennas. The nanowire as a plasmonic cavity, a resonance occurs when the phase accumulated on a single round trip amounts to multiple of 2π. This phase is determined by the propagation constant of the plasmonic mode supported by the nanowire and an additional phase on reflection at the wire termination. By fitting many resonance positions with different nanowire lengths, the phase change on reflection is determined. Such results are obtained only for a few simplified geometries. Nanoantennas are made from an arbitrary stack of homogeneous disks. Increasing the radius of a single disk toward infinitely and increasing its thickness yielded the reflection coefficient of surface Plasmon polariton propagating along a single metallic interface at a planar termination. The obtained results were in good agreement with previous results. [ABSTRACT FROM AUTHOR]

We have studied transmission through surface disordered waveguides in general and a solid basis. Our results showed that desired transmission properties on a waveguide through the roughness of its boundaries can be obtained. This surface scattering approach predicted that how mode specific scattering lengths in waveguides depend on the details of system's surface roughness. It was shown that previously neglected square-gradient scattering mechanism and predicted that this new scattering mechanism has to be considered together with the conventional amplitude scattering mechanism. Square gradient scattering is related to higher order terms in the disorder strength it can be the major scattering mechanism in system with modest disorder. Surface scattering theory is for long range correlations, which seems to restrict its applicability to very long waveguides. We have extended this surface scattering theory to short, individual waveguides. We found that an observed shift of the amplitude scattering gap could be attributed to the nonvanishing disorder strength. We also found that short wave lengths can exhibit effects predicted for systems with long range correlations leading to drastic changes in their transmission properties. The obtained results were compared with previously obtained results of theoretical and experimental works and were found in good agreement. [ABSTRACT FROM AUTHOR]