Large-area inverse opal structures in a bulk chalcogenide glass by spin-coating and thin-film transfer

Abstract

Large (cm×cm), uniform-thickness areas of an inverse-opal photonic crystal and an inverse-opal monolayer were fabricated in a high-refractive-index As30S70 chalcogenide glass. We have developed an effective low-cost, solution-based process for fabrication of photonic structures in chalcogenide glass from silica-colloidal-crystal thin-film templates (multi- and monolayer). The chalcogenide-glass solution is spin-coated over the silica-opal film template and the infilled composite structure (chalcogenide/opal) is then lifted-off and transferred onto the chalcogenide-glass disc at 225°C, followed by removal of the template in hydrofluoric acid. The extra step introduced in this work (lift-off and transfer) allows a reproducible and large-area structure to be fabricated on a bulk chalcogenide glass. Complete infilling of the silica template is possible due to the nano-colloidal nature (particle size 2–8nm) of the chalcogenide-glass solution and effective solvent release from the spin-coated chalcogenide film during post-annealing. The resulting chalcogenide-glass inverse-opal multilayer exhibits a Bragg peak at 670nm with a reflectance 70%, while the inverse-opal monolayer shows anti-reflectance behaviour <2% in the near-infrared region (1215–1660nm).