Micro lens arrays made by CO2-laser radiation

Abstract

In this article a new way of fabricating micro-optics, especially micro lens arrays (MLA’s) with lens heights up to several hundreds of micrometers is shown. Existing methods of MLA fabrication are compared to the new approach. Also applications are presented. A novel short pulse CO2-laser system is used for the production, which allows pulse lengths down to 200 ns. In combination with a common galvo-scanner system, the micro lenses are preformed by an ablation process in tens of seconds. Here, different lens diameters, lens radii and array sizes can be produced. In a second step, the MLA is fire-polished with the same laser source. For this process step the laser is switched to cw-mode. The preformed lenses melt and get a defined radius as a result of the surface tension of the molten glass. Measurements of the resulting geometry are be presented. As the results show, the laser based micro lens array fabrication process has a high reproducibility, very high flexibility, short process times and can process different glasses like borosilicate, soda lime or fused silica.