Bossi, Mariano L.Mariano L.BossiFölling, JonasJonasFöllingDyba, MarcusMarcusDybaWestphal, VolkerVolkerWestphalHell, StefanStefanHell2017-09-072017-09-072006https://resolver.sub.uni-goettingen.de/purl?gro-2/1120We demonstrate the breaking of the diffraction resolution barrier in far-field fluorescence microscopy by photoswitching ensembles of optically bistable organic molecular markers from a non-fluorescent to a fluorescent state and back. The photoswitching is accomplished by an isomerization reaction of a photochromic compound serving as a reversible energy acceptor of a fluorescent compound. The surpassing of the diffraction barrier with power levels of only a few hundred W cm(-2) of continuous wave irradiation is evidenced both in the effective point spread function and in the fluorescence images of test samples.enBreaking the diffraction resolution barrier in far-field microscopy by molecular optical bistabilityjournal_article10.1088/1367-2630/8/11/2750002425489000033143590