Fabrication and characterization of micro-structures created by direct laser writing in multi-layered chalcogenide glasses

摘要

Arsenic trisulfide (As_2S_3) is a chalcogenide (ChG) material with excellent infrared (IR) transparency (620 nm to 11 μm), low phonon energies, and large nonlinear refractive indices. These properties directly relate to commercial and industrial applications including sensors, photonic waveguides, and acousto-optics. Multi-photon exposure can be used to photo-pattern thermally deposited As_2S_3 ChG glassy films of molecular clusters. Immersing the photo-patterned cross-linked material into a polar-solvent removes the unexposed material leaving behind a structure that is a negative-tone replica of the photo-pattern. Nano-structure arrays that were photo-patterned in single-layered As_2S_3 films through multi-photon direct laser writing (DLW) resulted in the production of nano-beads as a consequence of a standing wave effect. To overcome this effect, an anti-reflective (AR) layer of arsenic triselenide (As_2Se_3) was thermally deposited between the silicon substrate and the As_2S_3 layer, creating a multi-layered film. The chemical composition of the unexposed and photo-exposed multi-layered film was examined through Raman spectroscopy. Nano-structure arrays were photo-patterned in the multi-layered film and the resulting structure, morphology, and chemical composition were characterized, compared to results from the single-layered film, and correlated with the conditions of the thermal deposition, patterned irradiation, and etch processing.