Fabrication of dual-wavelength diffractive beam splitters using maskless optical lithography with a digital micromirror device

In this paper, we demonstrate a dual-wavelength diffractive beam splitter to be used in parallel laser processing. The novel optical element, which is formed in a transparent material, generates two beam arrays at different wavelengths and allows their overlap at the process points on a workpiece. Since the splitter has a stochastically designed, complex, and deep surface profile, there is limited freedom in selecting a fabrication method. We designed the splitter using a simulated annealing algorithm and fabricated it in a photoresist through maskless exposure by using a digital micromirror device. We characterized the designed splitter, thereby corroborating the proposed beam-splitting concept.