Generation of nano-bumps on transparent quartz glass surface under femtosecond laser irradiation

Parallel surface patterning using micro particles is an attractive technique developed in recent years for large-area surface nanofabrication. It utilizes self-assembled particles lens-arrays, which convert the laser beam into a multiplicity of enhanced optical spots in parallel at focus. The focus of the particle is generally confined to a small region at the bottom of particle, which requires monolayer state of the particle array for efficient focusing. In this paper, we present a novel technique to tune the focusing properties of particle-lens array by changing the surrounding medium. It has been demonstrated to produce micro/nano convex bumps on transparent materials like quartz substrate.