Ultrafast laser processing of transparent materials

The advantages of ultrafast laser processing of materials include a minimal thermal penetration region and low processing temperature, precision removal of material, and good-quality feature definition. In this paper, fs laser (800 rim, 100 fs) processing of transparent materials at different focus positions and different laser intensities is investigated. Different morphologies are presented and compared. It is found that at controlled laser fluences, both bowl-shape and hump-like microstructures can be produced at the material surfaces. The lengths of the cracks produced inside the bulk material were measured as a function of the focus positions. The physical mechanisms for the formation of different microstructures are discussed. To reduce the patterning size, we employ transparent particles as microlens on the surfaces by self-assembly. Parallel structures in nanometer scale were produced by single fs laser pulse irradiation. These nanostructures change their shapes at different laser energies. The optical near-field distribution around the particle was also calculated according to exact solution of light scattering problem.