Origination of free-form micro-optical elements using one- andtwo-photon grayscale laser lithography

We discuss and describe the development of an origination processfor planar free-form micro-optical elements from a given optical design.The targeted masters serve as origination structures for a roll-to-rollmass fabrication process. Specifically targeted are complex, opticallysmooth, surface relief structures with variable structure heights in therange of 1–20 µm, with typical lateral sizes of more than 5 µm. The areaof the targeted masters is in the range of 1cm2.The main part of the paper is devoted to the description of aself-developed grayscale laser direct-write platform enabling one- andtwo-photon absorption lithography, also in combination on one and the samesample. In the following, we describe both methods and show that both leadto excellent structural quality of surface micro-relief structures. As ashowcase of what the system can do in principle, we designed andfabricated free-form micro-optical elements to project light from an LEDas a defined light pattern onto a wall. The proper optical functionalityof the fabricated element was shown within a demonstratorsetup.