Spatially microstructured topology of chalcogenide glasses by a combination of the electrothermal process and selective etching for functional infrared media

Abstract

Chalcogenide glasses exhibit a wide transparency domain spanning from near infrared (IR) to mid-IR and thus, have become highly attractive optical materials in a range of applications. Controlling the topology of these glasses can be seen as a key aspect for the design of optical elements such as gratings, metasurfaces, waveguides, and other diverse refractive and diffractive optical components. Here, we demonstrate the structuring of large, millimeter square areas that have been structured at the micrometer scale employing an easy two-step process, incorporating a micro-poling step followed by immersion in an amine solvent. Ge-Sb-S-Na glasses have been investigated, and the influence of the sulphur and sodium content on the pre- and post-poling material dissolution response has been discussed. Three compositions of varying sulphur and sodium content were selected to study the influence of thermal poling using either a homogeneous or a structured electrode. It was found that either a large difference in dissolution rates of poled and unmodified regions or a large poled layer thickness leads to the generation of significant topological contrast. The origin of the poled region’s selective etching has been explained on the basis of a poling-induced density decrease. Finally, it was demonstrated that when the targeted resolution is micrometric, this rather easy process could be employed as an alternative to classical lithography techniques.