Surface plasmons enable the transmission of optical information in confined geometries, inaccessible for diffraction-limited
far-field light, while having high signal bandwidth and propagation speed like conventional optics. These
advantages have resulted in novel applications for surface plasmons, such as offset-apertured near-field scanning optical
microscope (NSOM) probes. A subwavelength aperture couples surface plasmons that illuminate the tip apex of an
adjacent metal-coated tip, which results in a single-lobed probing optical spot having a full-width half maximum
(FWHM) similar to the apex diameter. Since the surface plasmons converge at the apex, an offset-apertured probe
promises stronger localized electric fields than an apertured NSOM having comparable FWHM. Additionally, the
subwavelength aperture does not permit the passage of far-field light, reducing the background signal in comparison to
apertureless NSOM probes. For other applications, the ability to selectively switch a waveguide "on" or "off" is desired.
Optical-optical switching for selective surface plasmon coupling would ideally permit high-speed switching on a small
scale. Two nodes are presented as means to perform switching of four planar thin surface plasmon waveguides by
interfering TEM10, TEM01, and TEM00 light beams normally-incident upon a node. One node uses a flat-apexed
pyramidal reflector to reflect the incident light toward the waveguides' ends. An alternative node is a simple square
aperture, which couples surface plasmons through light diffraction at the aperture's edges. Individually turned-off
waveguides are shown to have their coupled power attenuated by at least -10 dB.