A team of scientists headed by Dr. Christoph Lienau of the Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy (MBI) in Berlin develops and utilizes novel nanoptical techniques for imaging structures that are many times smaller than the wavelength of light. The research is based on a special Scanning Near-Field Optical Microscope (SNOM), patented by MBI, providing extremely high optical resolution and flexible combination with different spectroscopic techniques. A microscope based on this patent was now built for the Research Centre Jülich (Forschungszentrum Jülich), where scientists will use it to examine optical absorption in thin nanostructured layers of silicon. These studies at the Jülich facility are aimed at increasing the efficiency of silicon-based thin-film solar cells.
“We need to know the local optical properties of the silicon structures”, says Jülich scientist Dr. Reinhard Carius. It is not sufficient to only know the morphology of the surface. Therefore, neither atomic-force microscopes nor other electron microscopes can help, because these yield information on the surface structure but only limited knowledge about their electro-magnetic properties. “The SNOM built by the colleagues at MBI allows us to investigate how light propagates in the silicon thin films”, says Carius. What’s more, the near-field microscope is highly versatile. Carius adds: “I know of no other place to get such a machine, that is why we asked the MBI to build a duplicate for us.”
So, what is it that makes scanning near-field optical microscopy so special? “We outsmart light with it”, says Dr. Christoph Lienau of the Max Born Institute. He and his colleagues have constructed the SNOM and got it patented. Lienau explains: “Normally, with visible light, one cannot image structures that are smaller than its wavelenght.” However, light can be regarded not only as a wave phenomenon but as a stream of particles as well. And these particles, called photons, go through seemingly impenetrable barriers. In quantum physics this is known as a tunneling process. “Photons are tunneling through tiny holes smaller than the wavelength of light”, explains Lienau, “and we count the photons and measure their properties.”
Dr. Christoph Lienau | alfa
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