The authors present a simple and efficient technique for laser writing of arbitrary nanopatterns across a large surface area without using projection masks. It is based on the unique near-field focusing effect of a self-assembled particle array on the surface interacting with an angular incident laser beam. The spot resolution can be down to 80 nm. More than 6 ϫ 10 6 nanolines and c-shaped uniform patterns were fabricated simultaneously over an area of 5 ϫ 5 mm 2 by a few laser shots.
This paper reports the formation of uniform single layer micro-patterns of graphene on a glass substrate using direct femtosecond laser cutting. The cutting of graphene was achieved in air and argon. By translating the graphene sample with respect to the laser beam, continuous micro-channels were carved. The cutting geometry can be controlled by varying the laser fluence and the scanning path. Also, 1∼2 μm wide graphene micro-ribbons were hatched out. The ablation threshold of graphene was determined to be 0.16∼0.21 J/cm 2 . With the laser fluence higher than the ablation threshold, graphene was ablated rapidly and removed completely without damaging the glass substrate. Atomic force microscopy (AFM) and Raman spectroscopy have been used to confirm the ablation of graphene. Time domain finite difference modelling was employed to understand the thermal history of the laser ablation process.
Based on medium-tuned optical field enhancement effect around a self-assembled particle-lens array (PLA) irradiated with a femtosecond (fs) laser source, we demonstrated that high-precision periodical array of micro/nano-structures can be readily fabricated on glass surface or inside glass in large areas in parallel without any cracks or debris. The technique has potential for rapid fabrication of three-dimensional structures in multiple layers inside glass.
Ablation with nanoscale spatial resolution needs special tools to overcome conventional diffraction limit. A few methods have been successfully applied for this purpose. These include: surface nanostructuring by laser illuminated tip; Nearfield Scanning Optical Microscopy (NSOM) nano-patterning; Surface nano-processing based on optical resonances and near-field effects with transparent particles as well as the field enhancement by plasmonic nanoparticles. All these methods permit localized laser ablation on the scale beyond 100 nm. In this paper we report our recent work related to field enhancement by laser illuminated tip, near-field laser ablation with transparent particles and field enhancement by plasmonic effects.
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