454 research outputs found
Purcell factor for point-like dipolar emitter coupling to 2D-plasmonic waveguides
We theoretically investigate the spontaneous emission of a point--like
dipolar emitter located near a two--dimensional (2D) plasmonic waveguide of
arbitrary form. We invoke an explicite link with the density of modes of the
waveguide describing the electromagnetic channels into which the emitter can
couple. We obtain a closed form expression for the coupling to propagative
plasmon, extending thus the Purcell factor to plasmonic configurations.
Radiative and non-radiative contributions to the spontaneous emission are also
discussed in details
Polarization state of the optical near-field
The polarization state of the optical electromagnetic field lying several
nanometers above complex dielectric structures reveals the intricate
light-matter interaction that occurs in this near-field zone. This information
can only be extracted from an analysis of the polarization state of the
detected light in the near-field. These polarization states can be calculated
by different numerical methods well-suited to near--field optics. In this
paper, we apply two different techniques (Localized Green Function Method and
Differential Theory of Gratings) to separate each polarisation component
associated with both electric and magnetic optical near-fields produced by
nanometer sized objects. The analysis is carried out in two stages: in the
first stage, we use a simple dipolar model to achieve insight into the physical
origin of the near-field polarization state. In the second stage, we calculate
accurate numerical field maps, simulating experimental near-field light
detection, to supplement the data produced by analytical models. We conclude
this study by demonstrating the role played by the near-field polarization in
the formation of the local density of states.Comment: 9 pages, 11 figures, accepted for publication in Phys. Rev.
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Internet and U.S. citizen militias
Smelser's theory of collective behavior holds that people join radical social movements because they experience strain. Among the most serious strains are anxieties that relate to one's social status and the roles that correspond to it. A social movement arises as a means of coping with these anxieties.
Militia presence and activity on the Internet (especially Usenet) is a phenomenon that can be studied within the framework of Smelser's theory. Militia watchers contend that those who join the militias have experienced the kinds of strain to which Smelser refers.
A content analysis of Internet traffic of U.S. militias provides a test of the general thesis outlined above. By analyzing Internet sites it is possible to examine whether militiamen have experienced strain, and whether the strain, together with other factors, influence an individual's decision to join the militia.
This dissertation was the first sociological study of American militias on the Internet and the first in which militias from all regions of the country was studied. Information was gathered on 171 militiamen who joined 28 militias.
A qualitative analysis of militia web sites and Usenet traffic (n=1,189 online documents) yielded answers to seven research questions. Most militiamen studied experienced some form of stress or strain prior to joining the militia. Within this context, three generalized beliefs arose to help explain this stress among those militiamen. Bureau of Alcohol, Firearms and Tobacco (BATF) raids at Ruby Ridge, Idaho and Waco, Texas were mentioned most often as movement precipitants. Based on the militiamen studied, the militia movement was Internet-driven, although a number of alternative media played a joint role in movement mobilization. On the basis of the cases studied, increased social control following the Oklahoma City bombing affected the direction of the movement as many militias went underground. Yet, Usenet traffic by and about militiamen rose significantly. Constitutionalism was the primary philosophical orientation of the militias in this dissertation; however, Christian Identity militias were growing in number and visibility
Low-Power consumption Franz-Keldysh effect plasmonic modulator
In this paper we report on a low energy consumption CMOS-compatible plasmonic modulator based on Franz-Keldysh effect in germanium on silicon. We performed integrated electro-optical simulations in order to optimize the main characteristics of the modulator. A 3.3 dB extinction ratio for a 30 µm long modulator is demonstrated under 3 V bias voltage at an operation wavelength of 1647 nm. The estimated energy consumption is as low as 20 fJ/bit
Atomic diffraction from nanostructured optical potentials
We develop a versatile theoretical approach to the study of cold-atom
diffractive scattering from light-field gratings by combining calculations of
the optical near-field, generated by evanescent waves close to the surface of
periodic nanostructured arrays, together with advanced atom wavepacket
propagation on this optical potential.Comment: 8 figures, 10 pages, submitted to Phys. Rev.
Sub-wavelength patterning of the optical near-field
We report the sub-wavelength patterning of the optical near-field by total internal reflection illumination of a regular array of resonant gold nano-particles. Under appropriate conditions, the in-plane coupling between Localized Surface Plasmon (LSP) fields gives rise to sub-wavelength light spots between the structures. Measurements performed with an Apertureless Scanning Near-Field Optical Microscope (ASNOM) show a good agreement with theoretical predictions based on the Green dyadic method. This concept might offer a convenient way to elaborate extended optical trap landscapes for manipulation of sub-micrometer systems.Peer ReviewedPostprint (published version
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