Double-layer metasurface for enhanced photon up-conversion

Abstract

We present a double-layer dielectric metasurface obtained by stacking a silicon nanodisk array and a silicon photonic crystal slab with equal periodicity on top of each other. We focus on the investigation of electric near-field enhancement effects occurring at resonant excitation of the metasurface and study its optical properties numerically and experimentally. We find that the major difference in multi-layer metasurfaces when compared to conventional single-layer structures appears to be in Rayleigh–Wood anomalies: they are split into multiple different modes, which are themselves spectrally broadened. As a proof of concept, we cover a double-layer metasurface with a lanthanide-doped up-conversion particle layer and study its interaction with a 1550 nm photoexcitation. We observe a 2.7-fold enhanced up-conversion photoluminescence by using the stacked metasurface instead of a planar substrate, although only around 1% of the up-conversion material is exposed to enhanced near fields. Two mechanisms are identified explaining this behavior: First, enhanced near fields when exciting the metasurface resonantly, and second, light trapping by total internal reflection in the particle layer when the metasurface redirects light into high angle diffraction orders. These results pave the way for low-threshold and, in particular, broadband photon up-conversion in future solar energy and biosensing applications.

Metasurface‐Enhanced Photon Upconversion upon 1550 nm Excitation

“…The observed emission enhancement effect at nonresonant AoIs might be attributed to both, better extractions of the upconverted photons from the nanostructured metasurface and light trapping in the β-NaYF 4 :Er 3+ NP layer that might be caused by total internal reflection of higher diffraction orders on the metasurface. [20] Figure 6b shows two UC emission spectra of NPs on metasurface (orange lines) and planar silicon (blue lines, 100 times magnified) for 8° AoI excitation. Hence, when exciting a metasurface resonance (which is indicated by a green star in Figure 3a) for an excitation power density of P exc = 52 W cm −2 , a vast difference in emission intensity is observed which reflects the effect of the enhanced near fields on the absorption of β-NaYF 4 :Er 3+ NPs.…”

“…(nano)concentration of light. [17][18][19][20] However, these works suffer from limited enhancement values [17,19,20] or employ small-scale plasmonic nanostructures, [18] severely restricting its practicability in photovoltaics and the bioassay technology. On the other hand, dielectric metasurfaces have recently attracted great attention due to their opportunity for low dissipative losses, large resonant enhancement of electromagnetic near fields, [21] and applicability on larger area.…”

Optical Metasurfaces for Energy Conversion

“…An integrated UC enhancement by a factor of 2400 has been observed in relation to the experiment performed under the same condition, but on a nonstructured substrate. In attempting to boost the local field enhancement, aiming at even stronger UC emissions, the same group designed another kind of metasurface, a double layer stack formed by a hexagonal lattice photonic crystal slab integrated with a structure very similar to the metasurface used in the previous case . Following the same approach, the stack metasurface was coated with a PDMS film containing Yb 3+ /Er 3+ codoped NaYF 4 nanocrystals.…”

“…In attempting to boost the local field enhancement, aiming at even stronger UC emissions, the same group designed another kind of metasurface, a double layer stack formed by a hexagonal lattice photonic crystal slab integrated with a structure very similar to the metasurface used in the previous case. 389 Following the same approach, the stack metasurface was coated with a PDMS film containing Yb 3+ /Er 3+ codoped NaYF 4 nanocrystals. Performing transmission spectroscopy with the coated and uncoated metasurfaces, intense spectra were recorded.…”

A metasurface-based electronically steerable compact antenna system with reconfigurable artificial magnetic conductor reflector elements

“…Metamaterials have been known to exhibit such beyond nature capabilities and have been used in various applications ranging from microwave to optical frequencies covering a wide range of implementations from metantennas, reflectarrays, radar cross-section reduction, terahertz sensors to optical super lenses. 14 , 15 , 16 , 17 , 18 , 19 , 20 To further understand how metamaterials can be used to realize AMCs, let us consider an electromagnetic wave traveling through a medium with intrinsic impedance . When this wave impinges on another medium with a different intrinsic impedance , it encounters discontinuity resulting in reflections.…”