Spatially Shaped Femtosecond Laser Pulses for Micromachining of Materials with Dielectric Microlenses

The incorporation of transparent dielectric microspheres into regular direct-laser write (DLW) systems brings resolution advantages for imaging and marking of materials with high spatial resolution. The objective is to exploit the optical near- and far-field generated by the laser pulse interacting with the microsphere in the vicinity of the substrate of interest, overcoming the classical diffraction limit. For marking applications, one of the biggest challenges includes the positioning of the microspheres at custom positions with high accuracy and reproducibility, especially in the axial direction, since the properties of the final modification, in particular its size, will be defined by the distance between sphere and substrate. Different techniques have been developed during the last decade, including the use of optical tweezers, cantilevers and customized holders [1], [2], all of them representing numerous engineering challenges that hinder their widespread use in large area marking applications.