
Micro-structuring of glassy carbon for precision glass molding of binary diffractive optical elements
Author(s) -
Karin Prater,
Julia Dukwen,
Toralf Scharf,
Hans Peter Herzig,
Sven Plöger,
Andreas Hermerschmidt
Publication year - 2016
Publication title -
optical materials express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 66
ISSN - 2159-3930
DOI - 10.1364/ome.6.003407
Subject(s) - materials science , optics , structuring , binary number , optical glass , optical materials , molding (decorative) , glassy carbon , diffraction , optoelectronics , composite material , physics , cyclic voltammetry , electrode , electrochemistry , arithmetic , mathematics , finance , quantum mechanics , economics
Precision glass molding is a more cost efficient process for the large volume manufacturing of highly complex optical surfaces than direct manufacturing. Glassy carbon (GC) molds are used for precision glass molding, because they can be operated at temperatures up to 2000 degrees C. Used today mainly for manufacturing aspheric lenses, we consider here material technology for diffractive optical element (DOE). For diffractive optics the surface structuring is in the micrometer range and a surface roughness Ra lower than 20 nm is required. We introduce a reactive ion etching process with a titanium hard mask. Fused silica (FS) molds with identical optical functionality were fabricated for comparison. All molds were used for precision glass molding of a low T-g glass L-BAL42. We will compare GC and FS as mold materials in terms of quality and robustness. Optical performance measurements of the molded glass DOEs are shown and are in good agreement with the theoretical predictions. The results confirm that precision glass molding based on GC molds is a very promising technology to economically fabricate small structures in glass for DOEs