Nanostencil lithography with scanning optical fiber tip

In this work, nanolithographic patterning by means of a nanostencil inscribed on an optical fiber tip is presented. One-shot registration of multiple-sized features within a 4 mu m diameter patterning circle has been experimentally tested on photoresist AZ5214E coated silicon substrate, with features as small as 160 nm beign obtained, replicating the original stencil with excellent agreement. The nanostencil was created by focused ion beam (FIB) milling, although other techniques such as femtosecond laser ablation or pattern transfer to fiber tip can also be employed. Stencils can be arbitrary or based on optical elementary designs such as line patterns, photonic crystals, Fresnel zone plates or photon sieve. Exact transfer of the inscribed pattern is obtained while in contact lithography, while proximity exposure enables complex modulation of the optical near-field by the phase and/or amplitude stencil mask. This allows for optical interference to occur, in full 3D space, rendering sub-wavelength spot focusing, annular pattern formation, as well as the formation of 3D complex shapes. Experimentally, a 405 nm laser beam with 17 mW power was launched into the core of UV-Visible single mode fiber (S405-XP) on which end a photon sieve was previously inscribed by FIB. This tip was scanned over the photoresist. Patterning consisted of 1D scans, for which a minimum line width of 350 nm was obtained. Additionally, step-and-repeat patterning of the photon sieve fiber tip stencil was performed with, all features down to 160 nm being clearly resolved.