Dresden 2020 – scientific programme

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 13: Focus: High-resolution Lithography and 3D Patterning (Part II) (joint session KFM/CPP/HL)

KFM 13.4: Talk

Thursday, March 19, 2020, 10:30–10:50, TOE 317

Mass-producible microoptical elements by injection compression molding and focused ion beam structured titanium molding tools — •Simon Ristok¹, Marcel Röder², Simon Thiele³, Mario Hentschel¹, Thomas Günther², André Zimmermann², Alois Herkommer³, and Harald Gießen¹ — ¹4th Physics Institute and Research Center SCoPE, University of Stuttgart, Germany — ²Hahn-Schickard, Stuttgart, Germany — ³Institute of Applied Optics and Research Center SCoPE, University of Stuttgart, Germany

Injection molded polymer is the material of choice for micro-optics used in mass producible devices such as smartphones or optical sensors. For feature sizes on the micrometer scale the molding tools are usually fabricated by nickel electroplating on a silicon master, which was previously structured by electron beam lithography and subsequent etching. In total, two inversion steps are necessary to transfer the structure from the silicon master to a plastic polymer part. Here, we introduce an alternative method that requires only a single inversion step. An extremely robust titanium molding tool is directly structured with high precision by focused ion beam milling. We demonstrate the fabrication of Fresnel lenses with 100 µm diameter and a maximum structure height of 1 µm. The inverse Fresnel lens structured into the titanium is transferred to polymer by injection compression molding, enabling rapid mass replication. We show that the optical performance of the molded Fresnel lenses is in good agreement with simulations, rendering our approach suitable for applications which require compact and high quality optical elements in large numbers.