Breaking the diffraction limit in far-field light microscopy by stimulated emission

Summary form only given. The advantage of far-field light microscopy over electron, X-ray, or scanning probe microscopes is the non-destructive imaging of the interior of biological specimens. In fact, focused light is the only means to visualise living biological specimens at the submicron scale in three dimensions. Not surprisingly, far-field light microscopy is still the most popular form of microscopy in biomedical research, whereby 80% of the observations are based on fluorescence. An obvious disadvantage of using focused light is the limited spatial resolution, which for more than a century has been paradigmatic. The best resolving far-field light microscopes, the laser scanning confocal and multiphoton excitation microscope enjoy increasing popularity both in biomedicine as well as in single molecule spectroscopy, however, the best resolution they can achieve is 200 nm in the lateral and 500 nm in the axial directions.