KEYWORDS: Waveguides, Polarization, Finite element methods, Geometrical optics, Near field optics, Dielectrics, Dielectric polarization, Near field, Silicon, Scattering
We discuss a new effect of optical forces, namely, the self-alignment or instability of two parts of a waveguide
broken by an offset and a gap. Using a mode matching technique, we investigate the case where there is no
gap and only an offset. It is shown that for a TE incident mode, self-alignment occurs for small values of the
waveguide thickness, whereas for large values, the system is unstable. For a TM incident mode, however, the
situation is reversed and the two parts tend to self-align for large values of the waveguide thickness. It is also
shown that the forces are due to the presence of both radiation modes, generated by the discontinuity, and
the guided mode. For a TM incident mode, polarization surface charges are formed, that may cause strong
self-alignment forces in both the transverse and longitudinal directions.
Optical metamaterials characterized by several unique properties are introduced and characterized. The structures
comprise continuous metal films sandwiched between dense periodic arrays of optically thin metal strips or patches
separated by a small distance. The structures' electromagnetic properties are described by means of a modification of the
cavity model typically used to characterized microwave patch antennas. It is shown that the presented structures can
operate as negative index metamaterials that comprise deeply subwavelength periodic unit cells, are tunable for
operation in the near-infrared and visible spectra, and can be manufactured using standard methods and materials. In
addition, the presented structures can operate as an optical filter that, due to the presence of several resonances, transmits
fields for certain (controllable) wavelength bands, which are (nearly) independent of the angle of incidence and
polarization. The presented structures also can support arbitrary polarized surface waves that can have a high
wavenumber and can exhibit unusual dispersion relations.
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