Titanium Dioxide Mono-Material Multilayer Optical Coatings

High Resolution Image Download MS PowerPoint Slide Advanced optical functionalities are typically achieved using interference multilayer coatings composed of alternating materials with contrasting refractive indices. Here, we propose a mono-material concept in which the required refractive-index contrast is generated within a single material through a multilayer stack of porous and dense microstructured titanium dioxide (TiO 2 ). A key challenge in such architectures is the deposition of dense layers on porous ones without intermixing or excessive roughness. To address this, titanate 2D nanosheets are introduced as an interfacial layer. To demonstrate this concept, a visible near-infrared optical filter was designed using optical simulations and experimentally realized. The desired refractive-index contrast was achieved by tuning the porosity of consecutive amorphous TiO 2 layers, with ∼1 nm crystalline Ti 0.87 O 2 titanate nanosheet interlayers enabling sequential stacking of dense and porous TiO 2 . This approach enabled the fabrication of a six-layer mono-material optical filter and establishes a sustainable strategy for designing versatile mono-material optical coatings.