title: Optical polymers with tunable refractive index for nanoimprint technologies.
abstract: In order to realize a versatile high throughput production of micro-optical elements, UV-curable polymer composites containing titanium dioxide nanoparticles were prepared and characterized. The composites are based on an industrial prototype epoxy polymer. Titanium dioxide nanoparticles smaller than 10 nm were synthesized by the nonaqueous sol method and in situ sterically stabilized by three different organic surfactants. The composites exhibit high transparency. Distinct alteration of optical transmission properties for visible light and near IR wavelength range could be avoided by adaption of the stabilizing organic surfactant. Most importantly, the refractive index (RI) of the composites that depends on the fraction of incorporated inorganic nanoparticles could be directly tuned. E.g. the RI at a wavelength of 635 nm of a composite containing 23 wt% titanium dioxide nanoparticles is increased to 1.626, with respect to a value of 1.542 for the pure polymer. Furthermore, it could be demonstrated that the prepared inorganic-organic nanocomposites are well suited for the direct fabrication of low-cost micro-optical elements by nanoimprint lithography. A low response of the optical composite properties to temperature treatment up to 220 °C with a shrinkage of only about 4% ensures its application for integrated micro-optical elements in industrial production.
authors.affiliation: Fraunhofer Institute for Integrated Systems and Device Technology (IISB), Erlangen, 91058, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Landwehr
authors.forename: R
authors.initials: R
authors.lastname: Fader
authors.forename: M
authors.initials: M
authors.lastname: Rumler
authors.forename: M
authors.initials: M
authors.lastname: Rommel
authors.forename: A J
authors.initials: AJ
authors.lastname: Bauer
authors.forename: L
authors.initials: L
authors.lastname: Frey
authors.forename: B
authors.initials: B
authors.lastname: Simon
authors.forename: B
authors.initials: B
authors.lastname: Fodor
authors.forename: P
authors.initials: P
authors.lastname: Petrik
authors.forename: A
authors.initials: A
authors.lastname: Schiener
authors.forename: B
authors.initials: B
authors.lastname: Winter
authors.forename: E
authors.initials: E
authors.lastname: Spiecker