Epitaxial KNbO3:Yb3+,Er3+ nanopattern for enhanced upconversion photoluminescence

Nanopatterned epitaxial films of upconversion (UC) materials are desirable for various applications such as display lighting, waveguides, and optical imaging. In this study, we demonstrate that a nanopatterned epitaxial film of a UC material can be fabricated by combining a sol-gel process and nanoimprint lithography. An epitaxial KNbO3:Yb3+,Er3+ film is grown on a lattice-matched SrTiO3 single-crystal substrate, which exhibits an approximately 70 times enhanced UC photoluminescence (PL) intensity compared to that of a non-epitaxial KNbO3:Yb3+,Er3+ film grown on a Si substrate. Moreover, the introduction of a nanopattern enhances the UCPL intensity similar to 20 times compared to that of a planar film with the same volume of material. Our study paves the way for a better fundamental understanding and expansion in the application of UC materials. (C) 2019 Elsevier B.V. All rights reserved.