Flexible fabrication of microlenses in polymer layers with excimer laser ablation

Excimer laser ablation is a valuable microfabrication technology, which is particularly well-suited for surface structuring of polymers because of their excellent UV absorption properties and highly non-thermal ablation behavior. In this paper, we propose a fabrication technique for microlenses and arrays of microlenses using this technology and report on the present status of experimental results. The process is based on scanning a polymer surface with a pulsed excimer beam along well-chosen multiple concentric contours and in this way microlenses of arbitrary shape can be realized. Although our current experimental results are limited to structures in polycarbonate, the technique can be applied to any material suitable for excimer ablation of microoptics. The choice of ablation parameters and the selection of contour speeds and radii are discussed. Optical performance and lens surface quality are evaluated by imaging experiments, scanning electron microscopy and profilometer measurements. Due to the non-contact and direct-write nature of laser ablation, the proposed technique offers—contrary to many competing microfabrication processes—the powerful ability to insert microoptical functionality on top of optoelectronic components in a late phase of a heterogeneous assembly.