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  • Triangular-Aperture Probe Boosts Resolution

Photonics Spectra
Feb 2003
Researchers at Universität Münster in Germany have demonstrated a probe for near-field scanning optical microscopy that effectively doubles resolution capability without compromising brightness. They presented the triangular-aperture probe in the Nov. 18 issue of Physical Review Letters.

To fabricate the probes, the researchers break a coverslip to yield a piece of glass with a sharp corner formed by three edges, then evaporate a 100-nm-thick aluminum film on the glass and attach it to a piezoelectric tuning fork. Squeezing the sharp corner against a flat glass surface removes some of the aluminum, creating a triangular hole, and a prism on the backside of the probe focuses laser light into the structure.

In a series of experiments, a 60 x 60 x 60-nm-aperture probe displayed an optical resolution better than 40 nm and a transmission coefficient of 10-4. The technique enables the fabrication of even smaller apertures, according to the researchers.

Acronym for profile resolution obtained by excitation. In its simplest form, probe involves the overlap of two counter-propagating laser pulses of appropriate wavelength, such that one pulse selectively populates a given excited state of the species of interest while the other measures the increase in absorption due to the increase in the degree of excitation.
1. In optics, the ability of a lens system to reproduce the points, lines and surfaces in an object as separate entities in the image. 2. The minimum adjustment increment effectively achievable by a positioning mechanism. 3. In image processing, the accuracy with which brightness, spatial parameters and frame rate are divided into discrete levels.
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