Molded anti-reflective structures of chalcogenide glasses for infrared optics by precision glass molding
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.