Peepshow for the nanowelt

With the help of a super lens, researchers observe tiny structures visually, which can no longer be solazed under a light microscope

A light microscope is a usable observation tool as long as the subject of the consideration does not shrink too much. Then unfortunately, the well nature of the light is noticeable – objects that are smaller than half the wavelength of the light used for observation, with such a microscope no longer no longer loseless.

Science has adopted this dilemma and invented, for example, scanning electron microscope or grid power microscope, which can also go the atomic structure of matter on the ground. However, each of these methods (again depending on the subject of the desire) has its disadvantages. Also visually one can scan in the smallest structures – with a method that calls optical near-field microscopy.

Peepshow for the nanowelt

Scheme of experimental construction

You use the so-called optical near field. The term circumscribes the fact that with events very clearly under the wavelength of light the classic diffraction laws no longer apply. Practically, this realization is implemented by leading a tiny probe as a light source point for point over the object to be imaged (it is a grid procedure). The resolution is largely limited by the geometry of the probe.

The brief description already shows that this method also has a disadvantage – it only forms the surface of the object. Researchers of the Max Planck Institute for Biochemistry in Martinsried and the University of Texas in Austin (USA) now present a procedure in the current ie of the Science Magazine Science, in the nano sector under the surface (DOI: 10.1126 / Science.1131025). The team relies around Thomas Dubner on a super lens – a lens that consists of material with negative refractive index.

The physics teacher at school has remained negligently that it would give rise to materials with such properties – after all, he was right that normally no negative refractive index has been found in nature. But there are clever scientists constructing so-called meta materials. The lenses built thereof have the advantage that they can also focus the optical near field.

That this also works practically has now prove the research team around Dubner: The scientists used a super lines consisting of a 440 nanometer thick monocrystalline silicon carbide membrane included in two silicon dioxide slices. As a super lens, this material is in the middle infrared area at wavelengths by 11 microns (11000 nanometers). This managed to dissolve 880 nanometers remote objects that were not coarse than a twentieth of the wavelength of the light used.

Scanning electron microscope recording of the object (A), visually with super lens image of the same (B) and control image (C) with light of other wavelength

From the results of another experiment, the researchers calculated that the Superlinse could improve the resolution of the system by a factor of 4. The scientists now hope to be able to improve the procedure – even with other superlines – in the future, that structures are optically observed, which other methods are not accessible.

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