title: Amplifying Excitation-Power Sensitivity of Photon Upconversion in a NaYbF4:Ho Nanostructure for Direct Visualization of Electromagnetic Hotspots.
abstract: Controlling excitation power is the most convenient approach to dynamically tuning upconversion that is essential for a variety of studies. However, this approach suffers from a significant constraint due to insensitive response of most upconversion systems to excitation power. Here we present a study of amplifying excitation power-sensitivity of upconversion in Ho3+ions through the use of a NaYbF4host. Mechanistic investigation reveals that the sensitive response of Ho3+upconversion to excitation power stems from maximal use of the incident energy enabled by concentrated Yb3+sensitizers. This allows us to sensitively tune the red-to-green emission intensity ratio from 0.37 to 5.19 by increasing the excitation power from 1.25 to 46.25 W cm-2, which represents a 5.6-fold amplification of the tunability (from 0.19 to 0.49) offered by Yb/Ho (19/1 mol %) codoped NaYF4. Our results highlight that the excitation-power sensitive upconversion emission can be exploited to experimentally visualize electromagnetic hotspots.
authors.affiliation: State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University , Hangzhou 310027, China.|Department of Physics and Materials Science, City University of Hong Kong , 83 Tat Chee Avenue, Hong Kong SAR, China.
authors.forename: Bing
authors.initials: B
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Modern Optical Instrumentation, Zhejiang University , Hangzhou 310027, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University , Hangzhou 310027, China.
authors.forename: Yao
authors.initials: Y
authors.lastname: Xiao
authors.affiliation: Department of Physics and Materials Science, City University of Hong Kong , 83 Tat Chee Avenue, Hong Kong SAR, China.
authors.forename: Xian
authors.initials: X
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Modern Optical Instrumentation, Zhejiang University , Hangzhou 310027, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Li
authors.affiliation: State Key Laboratory of Modern Optical Instrumentation, Zhejiang University , Hangzhou 310027, China.
authors.forename: Mingyu
authors.initials: M
authors.lastname: Li
authors.affiliation: State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University , Hangzhou 310027, China.
authors.forename: Xvsheng
authors.initials: X
authors.lastname: Qiao
authors.affiliation: State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University , Hangzhou 310027, China.
authors.forename: Xianping
authors.initials: X
authors.lastname: Fan
authors.affiliation: Department of Physics and Materials Science, City University of Hong Kong , 83 Tat Chee Avenue, Hong Kong SAR, China.|City Universities of Hong Kong Shenzhen Research Institute , Shenzhen 518057, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Wang