Diffractive gray scale masks for excimer laser ablation

A new type of gray scale mask capable of fabricating a variety of microstructures is presented and evaluated. The mask is entirely made of quartz and makes use of tailored diffractive gratings which deflect parts of the originally illuminating laser beam beyond the solid angle of the imaging system used. In application, the mask has been tested in static laser ablation of polycarbonate fabricating continuous topographies. The fabrication process of this new gray scale mask is described. The potential for high pulse energy laser applications is supported by ablation thresholds at 248 nm being as high as 20 J/cm2 for diffractive gratings made of crystalline quartz, and 14 J/cm2 for gratings in fused silica.