Abstract
Upconversion (UC) materials are promising for harvesting visual light. However, the efficiency of UC processes is very low when applied to practical devices. Therefore, we propose an array of UC nanocylinders on a gold substrate and induce electric dipole (ED) and magnetic dipole (MD) resonances to increase the UC process efficiency by increasing light-matter interactions via the nanostructures. The nanocylinders not only increase the absorption of infrared light with a wavelength of 980 nm but also enhance the emission of visible light with a wavelength of 660 nm through surface plasmons and electric dipole resonances. The absorbance of the UC material can be enhanced by coupling with the surface plasmons and coupling with the MDs of each nanocylinder. On the other hand, the emission of visible light can be largely enhanced by increasing the spontaneous emission rate of the Purcell effect in electric dipole resonances and tailoring the output efficiency of the emitted light. In summary, we obtained an absorption enhancement of ×7.3, an average effective upward emission enhancement of ×21, and an improved total UC process of the proposed nanocylinder of ×155.
Highlights
Upconversion (UC) materials absorb light with low energy and emit converted light with higher energy [1,2]
UC materials are have the potential to enlarge the finite spectral working range of the absorption band in practical devices, which is typically limited to visible light, so that it encompasses near infrared light
We introduced a nanocylinder composed of UC materials and a gold substrate to enhance the efficiency of the UC process
Summary
Upconversion (UC) materials absorb light with low energy and emit converted light with higher energy [1,2]. Owing to the dipole resonances in dielectric structures, we can influence the direction of scattered light, enhance the interactions between light and particles (e.g., absorption), or enhance the emission of light depending on the resonant wavelengths. Various devices such as thin absorbers [16,17,18,19], lenses [20,21], and reflectors [22,23,24] have been reported that implement Mie resonances and appear in dielectric nanostructures. The reference structure when only the upward emission of visible light is collectable and meaningful
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