Breaking the far-field diffraction limit in optical nanopatterning via repeated photochemical and electrochemical transitions in photochromic molecules.

By saturating a photochromic transition with a nodal illumination (wavelength, λ), one isomeric form of a small molecule is spatially localized to a region smaller than the far-field diffraction limit. A selective oxidation step effectively locks this pattern allowing repeated patterning. Using this approach and a two-beam interferometer, we demonstrate isolated lines as narrow as λ/8 (78 nm) and spacing between features as narrow as λ/4 (153 nm). This is considerably smaller than the minimum far-field diffraction limit of λ/2. Most significantly, nanopatterning is achieved via single-photon reactions and at low light levels, which in turn allow for high throughput.