O-FIB: far-field-induced near-field breakdown for direct nanowriting in an atmospheric environment

Nanotechnology: Better writing with light An optical version of Focused Ion Beam technology (FIB) allows nanoscale "writing" such as surface texturing, drilling and sculpting of materials to be performed in air, avoiding the need for a vacuum which limits the application of conventional FIB. The "Optical Far-field-Induced near-field Breakdown" (O-FIB) approach has been developed by Hong-Bo Sun of Tsinghua University and colleagues at Jilin University in China and Swinburne University of Technology in Austrilia. It works by creating nanoholes with a femtosecond laser, which is controlled by sophisticated optical effects. The process can cover larger areas than conventional FIB, and with a spatial resolution below 20 nanometres. The ability to be performed in an open atmosphere offers new possibilities for nanoscale writing. These range from working on industrial scale materials such as ship hulls, down to living tissues and cells. Nanoscale surface texturing, drilling, cutting, and spatial sculpturing, which are essential for applications, including thin-film solar cells, photonic chips, antireflection, wettability, and friction drag reduction, require not only high accuracy in material processing, but also the capability of manufacturing in an atmospheric environment. Widely used focused ion beam (FIB) technology offers nanoscale precision, but is limited by the vacuum-working conditions; therefore, it is not applicable to industrial-scale samples such as ship hulls or biomaterials, e.g., cells and tissues. Here, we report an optical far-field-induced near-field breakdown (O-FIB) approach as an optical version of the conventional FIB technique, which allows direct nanowriting in air. The writing is initiated from nanoholes created by femtosecond-laser-induced multiphoton absorption, and its cutting "knife edge" is sharpened by the far-field-regulated enhancement of the optical near field. A spatial resolution of less than 20 nm (lambda/40, with lambda being the light wavelength) is readily achieved. O-FIB is empowered by the utilization of simple polarization control of the incident light to steer the nanogroove writing along the designed pattern. The universality of near-field enhancement and localization makes O-FIB applicable to various materials, and enables a large-area printing mode that is superior to conventional FIB processing.