Modulatable optical radiators and metasurfaces based on quantum nanoantennas

Pai-Yen Chen and Mohamed Farhat

Phys. Rev. B 91, 035426 – Published 20 January 2015; Erratum Phys. Rev. B 91, 159904 (2015)

Abstract

We investigate the tunable and switchable optical radiators and metamaterials formed by metallic nanodipole antennas with submicroscopic gaps (1.2 nm), of which linear and third-order nonlinear quantum conductivities are observed due to the photon-assisted tunneling effect. The quantum conductivities induced at the nanogap are relevant to power dissipations, which can be enhanced by the strongly localized optical fields associated with the plasmonic resonance. We demonstrate that the scattering property of an individual quantum nanoantenna and the transparency of a metamasurface constituted of it can be tuned by electrostatically controlling the linear conductivity (electronic tuning) or by adjusting the irradiation intensity that varies the nonlinear quantum conductivity (all-optical tuning).

Received 11 October 2014
Revised 22 December 2014

DOI:https://doi.org/10.1103/PhysRevB.91.035426

Erratum

Erratum: Modulatable optical radiators and metasurfaces based on quantum nanoantennas [Phys. Rev. B 91, 035426 (2015)]

Pai-Yen Chen and Mohamed Farhat

Phys. Rev. B 91, 159904 (2015)

Authors & Affiliations

Pai-Yen Chen^1,* and Mohamed Farhat²

¹Department of Electrical and Computer Engineering, Wayne State University, Detroit, Michigan 48202, USA
²Division of Computer, Electrical, and Mathematical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955–6900, Saudi Arabia

^*Corresponding author: pychen@wayne.edu

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Issue

Vol. 91, Iss. 3 — 15 January 2015

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Images

Figure 1
Schematics of a metallic nanoantenna with submicroscopic gap, which makes a MIM (tunneling) nanojunction. (b) Energy band diagram for the electron photon-assisted tunneling process. (c) Modulatable metasurface using biased nanoantennas, where patterned graphene are used as transparent electrodes, with a ∼97.7% transparency at near-infrared and visible frequencies. (d) Nanocircuit model for the nanoantenna in (a); here $C_{g}^{}$ is the geometry-yielded nanocapacitor, $R_{Q}^{(1)}$ and $R_{Q}^{(3)}$ are quantum resistances related to the linear and third-order nonlinear quantum conductivities, and the intrinsic dipole impedance $Z_{dip}^{} = R_{rad}^{} + R_{loss}^{} - i X_{dip} .$
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Figure 2
(a) Quantum resistance versus frequency for different bias conditions. (b) Optical field enhancement inside the nanogap versus frequency for a nanoantenna with $L = 90 nm, 2 a = 10 nm,$ and $d = 1.2 nm,$ under different bias conditions; here solid lines and dots represent results obtained from the nanocircuit model in Fig. 1 and the full-wave simulation, respectively. Inset of Fig. 2 shows the electric field distributions in the near-field air gap.
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Figure 3
(a) Third-order nonlinear quantum conductivity $R_{Q}^{(3)}$ versus illumination intensity for the nanoantenna in Fig. 2 at the resonance frequency $f_{0} = 350 THz$ , under different dc bias conditions. (b) is similar to (a), but plotting the corresponding optical field enhancement.
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Figure 4
(a) Scattering cross section versus frequency for the nanoantenna in Fig. 3; we assume a linear optical regime, i.e., low illumination intensity, and vary the bias condition, and (b) is similar to (a), but for the nonlinear optical regime, i.e.. fairly high illumination intensity, varying the illumination intensity; the dc bias is fixed $V_{dc} = 2 V .$
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Figure 5
(a) Transmission (solid line) and reflection (dashed line) coefficients versus frequency for the optical metasurface in Fig. 1 at low illumination intensity, varying the bias conditions, and (b) is similar to (a), but for different levels of illumination intensities, under a fixed dc bias $V_{dc} = 2 V .$
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Figure 6
(a) Schematic of nanoholography using a metasurface formed by quantum nanoantennas; the blue-colored nanoantennas are unbiased and the red-colored nanoantennas are biased with $V_{dc} = 2.25 V .$ When a normal incident plane wave impinges such hologram, a focused light sheet will be produced. (b) Contours of the amplitude of electric fields (top view) in the zero-bias condition, at the illumination intensity $I_{inc} = 25 MW / c m^{2} .$ (c)–(e) are similar to (b), but with nanoantennas biased to achieve the digital hologram in (a), for different levels of illumination intensities: (c) $I_{inc} = 1 MW / c m^{2},$ (d) $I_{inc} = 10 MW / c m^{2},$ and (e) $I_{inc} = 25 MW / c m^{2} .$
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