M.Sc.

Rojacher, Cornelia

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  • Publication
    Precision Glass Molding of infrared optics with anti-reflective microstructures
    ( 2020)
    Rojacher, Cornelia
    ;
    Vu, Anh Tuan orcid-logo
    ;
    Grunwald, Tim
    ;
    Bergs, Thomas
    Highly precise infrared lenses are used in a broad range of optical systems such as night visions, thermal imaging or gas sensing. As most infrared materials (e.g. Germanium, Chalcogenide glass) suffer from high Fresnel reflection losses, the use of anti-reflective coatings is state of the art to overcome this issue. An alternative approach is the implementation of anti-reflective microstructures into molded infrared lenses. This shortens the process chain and enables many advantages for example regarding the monolithic optics design. Precision Glass Molding (PGM), a replicative manufacturing technology, allows the macroscopic lens molding and the replication of surface microstructures to be carried out simultaneously. While PGM is an established process for manufacturing glass optics in general, there is a lack of knowledge regarding the replication of microstructures. This leads to the necessity to further investigate the PGM process chain for molding microstructures. The current paper addresses the process chain of manufacturing anti-reflective optics by precision glass molding. Process simulations are presented by a multiscale approach. In order to prevent wear, a suitable anti-adhesive coating system for molding tools with regard to the special requirements of microstructured surfaces is introduced. The results of the molding experiments highlight the importance of a multiscale simulation approach and demonstrate the stability of the anti-reflective microstructure.
  • Publication
    Molded anti-reflective structures of chalcogenide glasses for infrared optics by precision glass molding
    ( 2019)
    Vu, Anh Tuan orcid-logo
    ;
    Rojacher, Cornelia
    ;
    Grunwald, Tim
    ;
    Bergs, Thomas
    Infrared (IR) optic holds a key element over a broad range of advanced optical systems such as thermal imaging, night visions or laser-based sensing. Most infrared optical materials like chalcogenide glasses, however, suffer great transmission losses due to their high refractive index. Therefore, antireflective (AR) surfaces are necessary to enhance the optical performance of the IR optics by suppressing undesirable reflection at the optical surfaces and thus increasing the transmission. The AR-coatings commonly used for IR lenses in the contemporary optic market are expensive and environmentally critical. Instead, Precision Glass Molding (PGM), a replicative manufacturing method for the production of highly precise glass optics, becomes a promising solution to fabricate the AR-nanostructures on the chalcogenide glasses in a cost-efficient manner. The PGM process development starts out a multiscale modeling of the molding process, by which the form accuracy of the molded glass lenses is predicted at macroscale while the replication of the AR-structure is visualized at nanoscale simulation. This simulation necessitates a newly developed thermal-mechanical constitutive model to represent thermo-viscoelastic behaviors of the chalcogenide glass. Experimental validations of the form accuracy and the replicated AR-structure of the molded lenses demonstrate essential benefits of the simulation model. This paper focuses on the process simulation as well as the subsequent steps of mold manufacturing and glass molding itself. The success of molding AR-structures by precision glass molding promisingly satisfies the increasing demands for the high volume production of inexpensive IR optical elements in today's optics and photonics markets.