At Photonics West 2019, the trade fair for optics and photonics taking place in San Francisco, Nanoscribe showcases multi-level diffractive optical elements (DOEs) that are fabricated by means of high resolution 3D printers Photonic Professional GT2. See Nanoscribe in booth #366 (South Hall).
The fabrication of multi-level DOE microstructures gains more and more attention, both in scientific research as well as for industrial applications. DOEs empower a variety of applications such as optical measuring systems, material processing, or security labels. When producing multilayered DOEs, conventional planar lithography methods follow several process steps. The Photonic Professional GT2 3D printer offers a cost-effective, straightforward and high-resolution production of functional DOE prototypes and polymer masters for subsequent mass replication, allowing even submicron features and complex relief patterns. The 3D printer provides a streamlined workflow for the fabrication of DOEs in a single printing step.
Left to right: A top view with gray-scale pixels exemplifies the height levels of a multi-level DOE. A 3D view of the DOE shows the height profile. The SEM image displays a 3D printed DOE pattern.
One-step 3D printing on the microscale
Diffractive optical elements, as exemplified in image 1, modify the profile of laser beams when passing through them. Thanks to the DOE microstructure pattern, a single laser beam can be transformed into any wanted intensity shape in the far field. With Nanoscribe’s 3D printer for microscale parts, multi-level DOE designs with small pixels down to few hundreds of nanometers can be manufactured in one printing step. By two-photon polymerization, the printer uses a laser beam focused into a photoresin which cures the fluid only within the tight focal point. The laser focus scans layer by layer and solidifies a 3D object or a DOE 2.5D relief structure. Once the microstructured part has been printed, it is treated with a developing bath to remove residual unpolymerized resin.
Straightforward 3D printing workflow
DOEs generate almost arbitrary light distributions owing to their thin microstructures. Their multi-level designs are challenging due to the complex and precise arrangement of single elements at highest resolution. For the fabrication of high-resolution DOEs Nanoscribe’s 3D printers offer a well-thought-out workflow that includes a DOE import tool, a software recipe for print preparation and ultra-precise 3D printing of DOEs. The printer software processes high resolution DOE designs in a similar way as the well-established STL import of 3D models. A phase distribution image of the DOE, computed by an external program, is imported directly by the printer software. Thus, the software calculates a height profile from the phase distribution, as seen in image 2. With the DOE software recipe the 3D printer transforms the DOE design in an optimized microrelief pattern.
DOE masters for mass replication
3D printed DOE prototypes can be applied directly for beam shaping, - homogenizing or - splitting. Moreover, they are also suitable as polymer masters for mass replication, fitting into standard industrial processes. For example, metal mold inserts of 3D printed DOEs are implemented for subsequent injection molding, hot embossing or nanoimprint lithography.