title: Femtosecond Nanostructuring of Glass with Optically Trapped Microspheres and Chemical Etching.
abstract: Laser processing with optically trapped microspheres is a promising tool for nanopatterning at subdiffraction-limited resolution in a wide range of technological and biomedical applications. In this paper, we investigate subdiffraction-limited structuring of borosilicate glass with femtosecond pulses in the near-field of optically trapped microspheres combined with chemical postprocessing. The glass surface was processed by single laser pulses at 780 nm focused by silica microspheres and then subjected to selective etching in KOH, which produced pits in the laser-affected zones (LAZs). Chemical postprocessing allowed obtaining structures with better resolution and reproducibility. We demonstrate production of reproducible pits with diameters as small as 70 nm (λ/11). Complex two-dimensional structures with 100 nm (λ/8) resolution were written on the glass surface point by point with microspheres manipulated by optical tweezers. Furthermore, the mechanism of laser modification underlying selective etching was investigated with mass spectrum analysis. We propose that the increased etching rate of laser-treated glass results from changes in its chemical composition and oxygen deficiency.
authors.affiliation: Moscow Institute of Physics and Technology , Institutskiy lane 9, Dolgoprudny, Moscow Region 141700, Russian Federation.|Semenov Institute of Chemical Physics RAS , Kosygina st. 4, Moscow 119991, Russian Federation.
authors.forename: A
authors.initials: A
authors.lastname: Shakhov
authors.affiliation: Semenov Institute of Chemical Physics RAS , Kosygina st. 4, Moscow 119991, Russian Federation.
authors.forename: A
authors.initials: A
authors.lastname: Astafiev
authors.affiliation: Semenov Institute of Chemical Physics RAS , Kosygina st. 4, Moscow 119991, Russian Federation.|Department of Chemistry, Moscow State University , GSP-1, Leninskiye Gory 1-3, Moscow 119991, Russian Federation.
authors.forename: A
authors.initials: A
authors.lastname: Gulin
authors.affiliation: Semenov Institute of Chemical Physics RAS , Kosygina st. 4, Moscow 119991, Russian Federation.|Department of Chemistry, Moscow State University , GSP-1, Leninskiye Gory 1-3, Moscow 119991, Russian Federation.|Institute of Problems of Chemical Physics RAS , Academician Semenov avenue 1, Chernogolovka, Moscow Region 142432, Russian Federation.
authors.forename: V
authors.initials: V
authors.lastname: Nadtochenko
keywords: AFM; TOF-SIMS; dielectric microspheres; femtosecond lasers; laser-assisted chemical etching; nanostructuring; near-field; optical trap