Abstract
The resolution of a far-field optical microscope is usually limited tod = λ(2n sinα) > 200 nm, withn sin α denoting the numerical aperture of the lens andλ the wavelength of light. Here, I will discuss lens-based fluorescence microscopy concepts that feature a resolving power on the nanoscale. All these concepts share a common basis: exploiting selected (pairs of) states and transitions of the fluorescent marker to neutralize the limiting role of diffraction[1, 2]. Specifically, the marker is switched between a bright and a dark state to detect the emission of adjacent features sequentially in time. The first viable concept of this kind was Stimulated Emission Depletion (STED) microscopy[3] where the diameter of the region (focal spot) in which the molecule can be in the fluorescent state follows . I is the intensity that drives a fluorophore from the bright fluorescent state to the dark ground state by stimulated emission.Is depends (inversely) on the lifetime of the states. ForI/Is → ∞, it follows that d → 0, meaning that the resolution can be molecular[4–6]. Altogether, far-field optical ‘nanoscopy’ is a fascinating development in optics with high relevance to the many areas of sciences, in particular the life sciences. Since it has already been a key to answering important questions in biology, and owing to its simplicity and commercial availability, I expect far-field fluorescence ‘nanoscopes’ to enter most cell biology and many nanoscience laboratories the near future[7].
© 2009 IEEE
PDF ArticleMore Like This
Stefan W. Hell
JSV1_3 European Quantum Electronics Conference (EQEC) 2009
Volker Westphal, Silvio O. Rizzoli, Marcel A. Lauterbach, Dirk Kamin, and Stefan W. Hell
NMA1 Novel Techniques in Microscopy (NTM) 2009
Stefan W. Hell and Marcus Dyba
QML5 Quantum Electronics and Laser Science Conference (CLEO:FS) 2003