Metasurface‐Enhanced Photon Upconversion upon 1550 nm Excitation

Abstract

Photon upconversion upon 1550 nm excitation is of high relevance for applications in the third biological excitation window, for photovoltaics beyond current limitations, and enables appealing options in the field of glass fiber telecommunications. Trivalent doped erbium ions (Er3+) are the material of choice for 1550 nm excited upconversion, however, they suffer from a low absorption cross‐section and a low brightness. Therefore, the ability of silicon metasurfaces to provide greatly enhanced electrical near‐fields is employed to enable efficient photon upconversion even at low external illumination conditions. Hexagonally shaped β‐NaYF4:Er3+ nanoparticles are placed on large‐area silicon metasurfaces designed to convert near‐infrared (1550 nm) to visible light. More than 2400‐fold enhanced photon upconversion luminescence is achieved by using this metasurface instead of a planar substrate. With the aid of optical simulations based on the finite‐element method, this result is attributed to the coupling of the excitation source with metasurface resonances at appropriate incident angles. Analysis of the excitation power density dependence of upconversion luminescence and red‐to‐green‐emission ratios enables the estimation of nanoscale near‐field enhancement on the metasurface. The findings permit the significant reduction of required external excitation intensities for photon upconversion of 1550 nm light, opening perspectives in biophotonics, telecommunication, and photovoltaics.

Optical Metasurfaces for Energy Conversion

“…A fraction of the observed resonances was associated with the Rayleigh-Wood anomaly provided by the metastructure, absent in the single layer metasurface investigated in the previous work, which presented the strongest field enhancement according to numerical simulations. Upon similar excitation conditions as in ref , UC emission intensities enhanced by a factor of 2.7 as compared to the single layer metasurface have been recorded, this being attributed to the synergetic effects of the enhanced local fields and light trapping by the resonant modes.…”

“…At some technologically relevant wavelengths, as ∼1550 nm, important for telecom and excitation of biological tissues in the third biological window, this codoping strategy is not effective and the Er 3+ ions need to be directly excited. A metasurface similar to the one described previously was used in ref for enhancing the UC emission of NaYF 4 nanocrystals, this time doped only with Er 3+ ions. Its design followed the holes (diameter: 400 nm) hexagonal array (lattice constant: 1000 nm) on a silicon layer (thickness: 53 nm), resulting in the appearance of resonances at 1551 nm, coincident with the excitation wavelength.…”

Simultaneously Achieving Multicolor Emission of Down‐Shifting and Up‐Conversion in Yb3+, Er3+ ‐Codoped Cs2NaGdCl6 Double Perovskites

“…Upconversion (UC) luminescence materials have garnered significant attention in display and bio-sensing applications due to the high color purity, long fluorescence lifetime, and low energy excitation. [20][21][22][23][24][25][26] NaGdF 4 and NaYF 4 , known for their low phonon energy, are suitable host for rare earth doping, while the core@shell structure usually is commonly employed to enhance luminescence and modulate emission color. However, the synthesis process for these materials is complex, involving nitrogen protection and high reaction temperature.…”

Formation of Au@Ag Bimetallic Nanoparticles via Ion Implantation and Its Effects on Boosting the Near-Infrared Emission of Er3+ Ions in Germanate Glass for Applications in Optical Amplifiers

“…Within the family of germanate glasses, GeO 2 -PbO glass doped with RE 3+ ions has shown promising spectroscopic properties, supported by the relatively low phonon energy, large optical transparency in the visible and infrared regions, good thermal stability, excellent RE 3+ ions solubility, and a high refractive index. − Er 3+ doping has been extensively investigated for the development of amplifiers used for telecommunication devices operating at 1530 nm, corresponding to 4 I 13/2 → 4 I 15/2 transition. However, the small optical absorption cross section and its only three energy levels diagram do not favor the optimization of its performance for optical amplification. − Codoping Er 3+ with sensitizing ions such as Yb 3+ has been proven to be effective in solving the drawbacks. The broad absorption band and the high absorption cross section of Yb 3+ ions around 970 nm induce an efficient Yb → Er energy transfer process, which depends on strict control of the donor and acceptor ratio.…”