Patterning of optical coatings by laser ablation for the fabrication of dielectric masks and diffractive phase elements

Abstract

Excimer laser ablation is a versatile method to generate 2- or 3-D microstructured devices for mechanics, fluidics, and optics. Particularly, if in 1-D the structure is predefined by a layer design, and the other two dimensions are defined in the layer ablation process by mask projection, very precise structure definition in three dimensions and ablated surfaces with optical quality can be achieved. By patterning optical layers or layer stacks, a variety of applications is possible. Two examples are demonstrated. 1. Dielectric masks (amplitude masks) are fabricated by structuring a highly reflective dielectric layer stack. These masks can be used in high power laser machining systems. 2. Diffractive optical elements (phase elements) are generated by structured ablation of a transparent layer. The performance of these elements in shaping excimer laser beams is demonstrated.