Optical tristability and ultrafast Fano switching in nonlinear magnetoplasmonic nanoparticles

Wenjing Yu, Pujuan Ma, Hua Sun, Lei Gao, and Roman E. Noskov

Phys. Rev. B 97, 075436 – Published 23 February 2018

Abstract

We consider light scattering by a coated magnetoplasmonic nanoparticle with a Kerr-type nonlinear plasmonic shell and a magneto-optic core. Such a structure features two plasmon dipole modes, associated with electronic oscillations on the inner and outer surfaces of the shell. Driven in a nonlinear regime, each mode exhibits a bistable response. Bistability of an inner plasmon leads to switching between this state and a Fano resonance (Fano switching). Once the external light intensity exceeds a critical value, the bistability zones of both eigenmodes overlap, yielding optical tristability characterized by three stable steady states for a given wavelength and light intensity. We develop a dynamic theory of transitions between nonlinear steady states and estimate the characteristic switching time to be as short as 0.5 ps. We also show that the magneto-optical effect allows red and blue spectral shifts of the Fano profile for right and left circular polarizations of the external light, rendering Fano switching sensitive to light polarization. Specifically, one can reach Fano switching for the right circular polarization while cancelling it for the left circular polarization. The results point to a class of ultrafast Fano switchers tunable by a magnetic field for applications in nanophotonics.

Received 28 May 2017

DOI:https://doi.org/10.1103/PhysRevB.97.075436

Physics Subject Headings (PhySH)

Magneto-optical effect Nonlinear optics Optical bistability Plasmonics

Nonlinear DynamicsPlasma PhysicsParticles & Fields

Authors & Affiliations

Wenjing Yu¹, Pujuan Ma¹, Hua Sun^1,*, Lei Gao^1,2,†, and Roman E. Noskov^3,4

¹College of Physics, Optoelectronics and Energy of Soochow University, Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006, China
²Jiangsu Key Laboratory of Thin Films, Soochow University, Suzhou 215006, China
³“Dynamics of Nanostructures” Laboratory, Department of Electrical Engineering, Tel Aviv University, Ramat Aviv, Tel Aviv 6139001, Israel
⁴“Nanooptomechanics” Laboratory, ITMO University, St. Petersburg 197101, Russia

^*hsun@suda.edu.cn
^†leigao@suda.edu.cn

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Issue

Vol. 97, Iss. 7 — 15 February 2018

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Images

Figure 1
Schematics of the problem: Left and right circularly polarized (LCP and RCP) light waves incident on a coated magnetoplasmonic nanoparticle (cross section is only shown for clarity). The efficiency of light scattering can be switched between weak- and strong-scattering regimes by using a bistable response of plasmons localized on the inner and the outer shell surface. The static magnetic field H removes the degeneracy in the scattering of LCP and RCP light, rendering nonlinear switching sensitive to the light polarization.
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Figure 2
(a) The electric field structure for the eigenmodes and the Fano mode of the core-shell particle when $η = 0.1$ . Mode labels correspond to (b). (b) Linear light scattering efficiency as a function of wavelength and aspect ratio in the logarithmic scale $[{log}_{10} (Q_{sc})]$ . (c)–(e) Scattering efficiency spectra at different external fields for $η = 0.1$ and $R = 30$ nm. Continuous blue and dotted red curves correspond to solutions given by the direct averaging [Eqs. (3) and (6)] and the dispersion relation method [Eq. (10)].
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Figure 3
(a), (b) Scattering efficiency spectra in the nonlinear regime for different values of the driving electric field. (c), (d) The average optical field in the shell as a function of the incident field for different wavelengths indicated in (a) and (b) by dashed lines. Vertical dashed lines indicate the fields for which (a) and (b) were plotted. All other parameters are the same as in Fig. 2.
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Figure 4
(a) The enhancement factor ${〈 {| E_{s} |}^{2} 〉}^{1 / 2} / E_{0}$ vs the wavelength in the linear and nonlinear regimes. (b) Bifurcation diagram showing bistability and tristability zones as functions of volume fraction $η$ and the incident field $E_{0}$ for $λ = 365 nm$ . The points $S_{1} – S_{4}$ correspond to the bistability thresholds marked in Fig. 3.
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Figure 5
(a) Linear and (b) nonlinear scattering efficiency spectra for right and left circularly polarized light in the presence of the MO effect. The inset shows the resonance lines for the inner plasmon in detail. (c) Bistability/tristability zones in $(E_{0}, λ)$ axes for nonmagnetic and magnetic ( $g = 0.3$ ) regimes. Magnetization just slightly shifts the bistability zone for the outer plasmon (unnoticeable in a logarithmic scale). For all figures, $η = 0.1$ .
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Figure 6
Temporal dependencies of the scattering efficiency and the dimensionless driving field (orange). The signal pulse provokes a transition from a weak-scattering to a strong-scattering state for $g = 0$ (black) and $g = 0.3$ in the case of a right circularly polarized light (red). For a left circularly polarized light, the system returns to the initial state (blue). The parameters are $E_{0} = 50 statvolt / cm$ (the background field), $E_{p} = 1265 statvolt / cm$ (the pulse peak field), and $λ = 358 nm$ .
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