Triangular-Aperture Probe Boosts Resolution
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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