One of the most important features in near-field optics is the total amount of near-field light that can be coupled through an extremely small aperture. As mentioned previously, optical throughput of these microfabricated aperture probes is very high due to the geometric structure of the SiO

tip. However, optical throughput drastically decreases with decreasing aperture size, especially for apertures smaller than 100 nm (see Figure 5.2). To extend this application into other areas optical throughput needs to be improved.