PERCOLATION THRESHOLD: A NOVEL NONLINEARITY FOR BREAKING THE DIFFRACTION LIMIT IN PHOTOLITOGRAPHY

DARÍO KUNIK; OSCAR E. MARTÍNEZ

Buenos Aires Argentina

Conferencia; 10th International conference on near-field optics, nanophotonics and related techniques; 2008

In a recent work [1] we have shown a technique that yields sub-diffraction limited nanostructure by two-photon polymerization. The structures are generated by exciting a photo-initiator uniformly diluted in volume, and the resulting structure has a 20nm height, well below the field of focus of the excitation beam. In this work we show that if the surface concentration of photo-initiators is adequate, the surface percolation threshold occurs before the bulk percolation takes place, hence originating a surface structure with a size determined by the density of initiator. As the excitation power or exposure time is increased the volume percolation onset creates a massive structure of the size of the optical beam excitation volume. We performed a simple 3rd-neighbors percolation model with particle sizes depending on the pump energy density that describe the experimental results obtained.