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Nanomechanical electro-optical modulator based on atomic heterostructures

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ABSTRACT

Two-dimensional atomic heterostructures combined with metallic nanostructures allow one to realize strong light–matter interactions. Metallic nanostructures possess plasmonic resonances that can be modulated by graphene gating. In particular, spectrally narrow plasmon resonances potentially allow for very high graphene-enabled modulation depth. However, the modulation depths achieved with this approach have so far been low and the modulation wavelength range limited. Here we demonstrate a device in which a graphene/hexagonal boron nitride heterostructure is suspended over a gold nanostripe array. A gate voltage across these devices alters the location of the two-dimensional crystals, creating strong optical modulation of its reflection spectra at multiple wavelengths: in ultraviolet Fabry–Perot resonances, in visible and near-infrared diffraction-coupled plasmonic resonances and in the mid-infrared range of hexagonal boron nitride's upper Reststrahlen band. Devices can be extremely subwavelength in thickness and exhibit compact and truly broadband modulation of optical signals using heterostructures of two-dimensional materials.

No MeSH data available.


Device characterization using spectroscopic ellipsometry.(a) Ellipsometric reflection spectrum Ψ of our graphene/hBN/plasmonic heterostructure (Vg=0 V, θ =70°). (b) Colour map of Ψ as a function of wavelength and Vg.
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f2: Device characterization using spectroscopic ellipsometry.(a) Ellipsometric reflection spectrum Ψ of our graphene/hBN/plasmonic heterostructure (Vg=0 V, θ =70°). (b) Colour map of Ψ as a function of wavelength and Vg.

Mentions: Devices were studied using spectroscopic ellipsometry and reflectometry (see Methods). Figure 2a shows the ellipsometric reflection spectrum (Ψ) of a device from the mid-ultraviolet through to the near-infrared, when illuminated at an incident angle of θ=70°. We attribute the broad absorption peaks in the wavelength range 280 nm<λ<590 nm to Fabry–Perot (FP) interference in the air gap, whereas the sharp feature at λ=275 nm is caused by the complex, multi-peaked ultraviolet absorption spectrum of hBN28. The remaining strong features from 590 nm<λ<1,600 nm primarily arise from the nanoarray and correspond to the Rayleigh cutoff wavelengths for air, determined by , where a is the array periodicity, m is an integer and n the refractive index of air5. The absorption peaks at λ≈620, 780, 1,030 and 1,520 nm can be associated with the m=5, 4, 3 and 2 diffraction-coupled modes, respectively. The m=4, 5 features each consist of two peaks because of a mismatch between the inverse polarizability and retarded dipole sum of individual nanoparticles in the plasmonic nanoarray in this spectral region29, caused by the presence of the hBN.


Nanomechanical electro-optical modulator based on atomic heterostructures
Device characterization using spectroscopic ellipsometry.(a) Ellipsometric reflection spectrum Ψ of our graphene/hBN/plasmonic heterostructure (Vg=0 V, θ =70°). (b) Colour map of Ψ as a function of wavelength and Vg.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5121424&req=5

f2: Device characterization using spectroscopic ellipsometry.(a) Ellipsometric reflection spectrum Ψ of our graphene/hBN/plasmonic heterostructure (Vg=0 V, θ =70°). (b) Colour map of Ψ as a function of wavelength and Vg.
Mentions: Devices were studied using spectroscopic ellipsometry and reflectometry (see Methods). Figure 2a shows the ellipsometric reflection spectrum (Ψ) of a device from the mid-ultraviolet through to the near-infrared, when illuminated at an incident angle of θ=70°. We attribute the broad absorption peaks in the wavelength range 280 nm<λ<590 nm to Fabry–Perot (FP) interference in the air gap, whereas the sharp feature at λ=275 nm is caused by the complex, multi-peaked ultraviolet absorption spectrum of hBN28. The remaining strong features from 590 nm<λ<1,600 nm primarily arise from the nanoarray and correspond to the Rayleigh cutoff wavelengths for air, determined by , where a is the array periodicity, m is an integer and n the refractive index of air5. The absorption peaks at λ≈620, 780, 1,030 and 1,520 nm can be associated with the m=5, 4, 3 and 2 diffraction-coupled modes, respectively. The m=4, 5 features each consist of two peaks because of a mismatch between the inverse polarizability and retarded dipole sum of individual nanoparticles in the plasmonic nanoarray in this spectral region29, caused by the presence of the hBN.

View Article: PubMed Central - PubMed

ABSTRACT

Two-dimensional atomic heterostructures combined with metallic nanostructures allow one to realize strong light&ndash;matter interactions. Metallic nanostructures possess plasmonic resonances that can be modulated by graphene gating. In particular, spectrally narrow plasmon resonances potentially allow for very high graphene-enabled modulation depth. However, the modulation depths achieved with this approach have so far been low and the modulation wavelength range limited. Here we demonstrate a device in which a graphene/hexagonal boron nitride heterostructure is suspended over a gold nanostripe array. A gate voltage across these devices alters the location of the two-dimensional crystals, creating strong optical modulation of its reflection spectra at multiple wavelengths: in ultraviolet Fabry&ndash;Perot resonances, in visible and near-infrared diffraction-coupled plasmonic resonances and in the mid-infrared range of hexagonal boron nitride's upper Reststrahlen band. Devices can be extremely subwavelength in thickness and exhibit compact and truly broadband modulation of optical signals using heterostructures of two-dimensional materials.

No MeSH data available.