Rapid prototyping of 1xN multifocus gratings via additive direct laser writing

Abstract

Multifocus gratings (MFGs) enable microscopes and other imaging systems to record entire Z-stacks of images in a single camera exposure. The exact grating shape depends on microscope parameters like wavelength and magnification and defines the multiplexing onto a grid of MxN Z-slices. To facilitate the swift production and alteration of MFGs for a system and application at hand, we have developed a fabrication protocol that allows manufacturing of 1xN MFGs within hours and without the requirement of clean room facilities or hazardous etching steps. Our approach uses photolithography with a custom-built stage-scanning direct laser writing (DLW) system. By writing MFG grating lines into spin-coated negative tone SU-8 photoresist, polymerized parts are crafted onto the substrate and thus directly become a part of the grating structure. We provide software to generate the required MFG grating line paths, details of the DLW system and fully characterize a manufactured MFG. Our produced MFG is 5.4 mm in diameter and manages to record an image volume with a Z-span of over 600 μm without spherical aberrations or noticeable loss of resolution.