Far-Field Parallel Direct Writing of Sub-Diffraction-Limit Metallic Nanowires by Spatially Modulated Femtosecond Vector Beam

Metallic nanowires have exhibited paramount importance in achieving functional electrical, electrochemical, and optical performances due to their unique physicochemical properties. Efficient fabrication of the nanowires with controllable geometry and line width is highly required in related applications. Here a new far-field laser parallel direct writing approach for fabricating nanowire array far beyond the diffraction limit by a modulated vector beam with dual-peak intensity distribution is reported. Such a modulated beam can perform selective laser ablation to fabricate nanowires, whose line width can be largely reduced by tuning the dual-peak orientation relative to the laser scanning direction. As a demonstration, a 157 nm-wide (less than lambda/3) gold nanowire, reaching approximate to 1/20 of the diffraction limit, has been fabricated in far field by using a low numerical aperture microscope objective (NA = 0.1). The nanowire fabrication efficiency is also largely improved by applying multifocal modulated vector beams for parallel processing.