65 nm feature sizes using visible wavelength 3-D multiphoton lithography.

Nanoscale features as small as 65 +/- 5 nm have been formed reproducibly by using 520 nm femtosecond pulsed excitation of a 4,4'-bis(di-n-butylamino)biphenyl chromophore to initiate crosslinking in a triacrylate blend. Dosimetry studies of the photoinduced polymerization were performed on chromophores with sizable two-photon absorption cross-sections at 520 and 730 nm. These studies show that sub-diffraction limited line widths are obtained in both cases with the lines written at 520 nm being smaller. Three-dimensional multiphoton lithography at 520 nm has been used to fabricate polymeric woodpile photonic crystal structures that show stop bands in the near-infrared spectral region.