| Across the different fields of science researchers strive to investigate and manipulate more basic physical systems at the nanoscale level. This is particularly challenging to do optically, because as systems approach dimensions close to the wavelength of light, diffraction limits the resolution that can be achieved with conventional optics to approximately lambda/(2nsintheta). However, due to existence of one or more evanescent components, near-field light can obtain spatial resolution that exceeds the diffraction limit.; One method for overcoming this limit is operating in the near-field of a sub-wavelength aperture. Unfortunately, it has been shown that the power throughput of apertures smaller than a wavelength falls off as (d/lambda) 4. I have designed, classified, and fabricated resonantly shaped apertures, for use in the optical regime that overcome this rapid falloff. Prior work showed that this approach was practical at microwave frequencies. Operating at optical frequencies, however, presents many challenges. In particular, optical properties of metals, topological artifacts introduced by fabrication, and the strong coupling with measurement probes must be understood and accounted for in order to design apertures properly and interpret results.; Individual transmission spectra taken using confocal spectroscopy showed that C-shaped apertures exhibited from 13--22 times enhancement over square apertures of the same area, implying a 106 improvement over a square aperture modeled to produce the same near field spot size. A photon scanning tunneling microscope was used to characterize the near-field performance of our C-apertures, and a sub-wavelength spot size was verified for these structures. Calibration studies were carried out to deconvolve the images with the preferential collection efficiency of the probe, and its finite collection range. A general formalism was developed for quantitative interpretation of near-field images. Numerical studies were carried out on fractal configurations of nano-apertures which were shown to elicit throughput enhancements an order of magnitude larger and several times improvement in achievable resolution. Applications of these designs will also be presented from several areas including near-field data storage and lithography, nano-scale optical trapping, and enhanced near-field probe manufacturing. |
