The resolution of optical patterning is constrained by the far-field diffraction limit. In this letter, we describe an approach that exploits the unique photo- and electro-chemistry of diarylethene photochromic molecules to overcome this diffraction limit and achieve sub-wavelength nanopatterning.

The ability to pattern nanometric features on various substrates with high throughput, accuracy, and uniformity is the key driving force enabling novel applications in nanophotonics, nanoelectronics, nano-electro-mechanical systems, and nanofluidics. Patterning via Optical Saturable Transitions (POST) is an optical nanopatterning technique that circumvents the far-field diffraction limit by exploiting the linear switching properties of thermally stable photochromic molecules. Previously, POST was enabled by an electrochemical oxidation “locking step.” In this letter, we report an electrode-free “locking step” that exploits the difference in solubility between the two isomeric states of a photochromic molecule in a polar solvent. The reported method obviates the need for a conducting underlayer and also reduces the number of required steps. Using this method, we demonstrated isolated lines of width ∼λ/4 and spacing between features as small as ∼λ/2.5 for an exposure wavelength of λ.

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Fabrication of transferrable, fully suspended silicon photonic crystal nanomembranes exhibiting vivid structural color and high-Q guided resonance

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