WESTERN ILLINOIS UNIVERSITY, PHYSICS, MACOMB, IL 61455
For many years, applying microscopy with focused light meant that details smaller than half the wavelength of light (200 nm) could not be resolved. Today, it is known that using conventional optics it is possible to image at least fluorescent samples with a level of detail far below the diffraction limit. Stimulated Emission Depletion (STED) microscopy and newer far-field optical approaches can provide resolutions better than 20 nm, and in principle are able to resolve molecular detail. Thus far-field optical nanoscopy ushers in non-invasive access to the nanoscale of the living cell.
While the diffraction barrier has motivated the invention of electron, scanning probe, and x-ray microscopy, in the life sciences 80% of all microscopy studies are still performed with lens-based (fluorescence) microscopy. The reason is that the 3D imaging of the interior of (live) cells requires the use of focused visible light. Hence, besides being a fascinating physics endeavor, the development of a far-field light microscope with nanoscale resolution would facilitate observing the molecular processes of life. In this presentation, I will discuss novel physical concept of the STED, which radically breaks the diffraction barrier in focused fluorescence microscopy. The strategy in this concept exploits selected molecular transitions of the fluorescent marker to neutralize the limiting role of diffraction.
[Abstract (DOCX)]