For nearly a century, dielectric materials have been used to produce thin film filters capable of precisely modifying electromagnetic wave interactions at material boundaries. Minimizing visible reflections from optical elements is the most mature use of these techniques, but modern applications often require advanced filters that operate in the ultraviolet or infrared regions. Vapour deposition is the dominant coating technology used to produce these filters, but sol-gel processes have also gained a footing. These methods have been used to create organic/inorganic hybrids that can theoretically withstand larger strains than a purely inorganic metal oxide, but demonstrations of thin film filters with strain properties similar to pure polymers have been sorely lacking. A homogeneous composite featuring inorganic nanoparticles in a polymer matrix is capable of very high strains without failure. We demonstrate such a system here with a 38-layer nanocomposite filter that is subjected to 20% strain with simultaneous evaluation of optical performance. The filter's reflectance peak shifts toward the shorter wavelengths as film thickness decreases in response to the strain, but the peak intensity of the reflected light does not substantially change. These results suggest that the nanocomposite layers are behaving as homogeneous materials with consistent optical parameters throughout the test.
Nanocomposites are created by doping host polymers with nanoparticles that typically have higher or lower refractive indices. The ability to tailor the mechanical and optical performance of these composites has led to their increased use in transparent materials. Nanocomposites maintain the elastic properties of the binding polymers and exhibit infinite refractive index tunability between the limits of the system. These unique properties provide distinct benefits for multilayer, thin-film optical filters. Because the nanoparticles are dispersed in a fluid or bound in a polymer matrix in use, toxicity risks that may be associated with raw particles are reduced. Using a stable dispersion of titanium dioxide nanoparticles and a UV curable monomer, we were able to design and produce several quarter-wave filters that demonstrate control of the height and width of the passband through adjustment of the organic/inorganic ratio and layer count. The volume loading of the metal oxides can be adjusted from zero to near the theoretical packing density of spheres, allowing refractive index to be controlled over a large range. Because metal oxide particles exhibit high UV absorption, these additives provide UV protection to the host polymer and the filter's substrate. Additionally, significant improvements in abrasion resistance are often observed in films loaded with nanoparticles at the concentrations of interest.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.