Fabrication of micro-optical elements in fused silica with laser backside etching(Laser processing)

Abstract

One of the urgent challenges of current laser material processing is the high quality and precise etching of transparent materials for, e.g., microoptical applications. Indirect laser processing techniques such as LIBWE and LESAL (laser-induced backside wet etching, laser etching at a surface adsorbed layer, respectively) allow the accurate etching of transparent materials like fused silica at low laser fluences, with etch rates in the nanometer scale and a low roughness. In combination with established laser processing techniques, e.g., mask projection, scanning contour mask technique, and direct writing, these etch techniques allow the direct machining of dielectric materials with almost optical quality. The etching of diffractive and refractive topographies for micro prism arrays, free-form surfaces, as well as periodically sub-micron structures with nanometer depth accuracy and a low roughness is demonstrated.