News and Reviews (May 2018)

3D Printing of Diffractive Optical Elements

Nanoscribe’s Solutions for Direct DOE Fabrication

Diffractive optical elements – shortly called DOEs - generate almost arbitrary light distributions in the far-field. They can be used for beam shaping, -homogenizing or -splitting. 3D microprinting offers a quick, cost-effective workflow for producing optically complex prototypes and polymer masters of DOEs, for example, for security features in transparent windows of some bills. Both binary and multilevel 2.5D DOEs benefit from the 3D fabrication capabilities and submicron resolution offered by Nanoscribe’s Photonic Professional GT 3D printers.

In comparison to conventional planar lithography methods that require several lithography steps when making non-binary DOEs, 3D microprinting enables the direct fabrication of multilayer DOEs in a single printing step. This technique is straightforward and makes functional DOE prototypes available without costly and lengthy mask making. For this purpose, Nanoscribe has developed a simplified workflow specifically designed for the printing of DOEs. More clearly, the DOE workflow presented with the printer Photonic Professional GT includes a DOE import tool, a software recipe for print preparation and the precise fabrication of the DOE.

For the print preparation of a DOE, a phase distribution image of the DOE will be required. This image must be computed by an external program. Once this is done, the printer software DeScribe can import the phase distribution image in the form of a bitmap and generate a height profile, as shown in the figures below. The import tool handles DOE designs in a similar manner as the STL import of 3D models, following the print preparation known from well-established 3D printer standards. A novel DeScribe recipe optimized for DOEs operating at 640 nm is at the user’s disposal as well. After the preparation, the 3D printer produces the designed DOE as a 2.5D relief structure.

Phase mask Nanoscribe.jpg

Nanoscribe_DeScribe_Height Profile

Left: Phase mask. Right: Height profile generated by printer software DeScribe.

Even complex DOE prototypes are printed this way. Nanoscribe’s 3D printing solutions secure a user-friendly workflow supported by smart software tools. Moreover, the 3D printing process meets the requirements of high axial as well as vertical resolution for diffractive optics. DOEs can either be printed for direct use as prototypes or as molding tools for series production. In this case, the 3D printed polymer part is used as a master for subsequent mass replication.

You can explore examples of 3D-printed diffractive optics in our application category “Diffractive Optical Elements”.

SEM image of DOE surface and diffraction image

Left: SEM Close-up view of DOE surface relief. Right: Diffraction image generated by a DOE replicated from a 3D printed part.