Fabrication Large-scale Diffractive Lens Arrays on Chalcogenide Glass by Means of Step-and-Repeat Hot Imprinting and Non-Isothermal Glass Molding

Abstract

In this study, a new cost-effective and high-precision process chain for the fabrication of large-scale diffractive lens arrays on chalcogenide glass is proposed. First, a positive diffractive lens array is fabricated on a PMMA master substrate by employing a step-and-repeat hot imprinting process. The direct hot imprinting can transfer the microstructures from a heated mold to the polymer substrate accurately. Repeating the hot imprinting process according to a predetermined path, the desired diffractive lens array is obtained. Unlike photolithography and electron-beam writing, which are expensive technologies with sophisticated process, the hot imprinting is an easier, cheaper and more eco-friendly method for fabricating diffractive features with continuous profile. Afterwards a casting process is applied to create a PDMS mold with the negative features. The diffractive lens array with continuous profile is successfully transferred from the master substrate to the PDMS elastomer, which is used as a mold for subsequent precision glass molding. Finally, the microstructures of PDMS mold are replicated to the chalcogenide glass by non-isothermal glass molding. In this process, the mold and workpiece are set at different temperatures. The PDMS mold at low temperature maintains enough rigidity, so as to press the features into the softened chalcogenide glass more easily, which is at relatively higher temperature, resulting in a positive high-fidelity diffractive lens array on the chalcogenide glass. Surface profiles and optical performance of the fabricated components are characterized quantitatively. Results showed that large-scale diffractive lens array with continuous profile can be successfully fabricated on Chalcogenide glass by this proposed process chain with high quality and integrity.