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Issue 17, 2019
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Highly tunable nonlinear response of Au@WS2 hybrids with plasmon resonance and anti-Stokes effect

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Abstract

We synthesize Au@WS2 hybrid nanobelts and investigate their third-order nonlinear responses mediated by a strong anti-Stokes effect. By using the femtosecond Z-scan technique and tuning the excitation photon energy (Eexc), we find the sign reversals of both nonlinear absorption coefficient β and nonlinear refractive index γ to be around 1.60 eV, which is prominently higher than the bandgap (1.35 eV) of WS2 bulk owing to the strong anti-Stokes processes around the bandgap of the indirect semiconductors. The saturable absorption and self-defocusing of the WS2 nanobelts are significantly enhanced by the plasmon resonance of the Au nanoparticles when Eexc > 1.60 eV. But the excited state absorption assisted by the anti-Stokes processes and the self-focusing observed at Eexc < 1.60 eV are suppressed by the surface plasmon. Furthermore, by using population rate equations, we theoretically analyze the sign reversals of both β and γ and reveal the physical mechanism of the unique nonlinear responses of the hybrids with the plasmon resonance and anti-Stokes effect. These observations enrich the understanding of the nonlinear processes and interactions between the plasmon and exciton and are helpful for developing nonlinear optical nanodevices.

Graphical abstract: Highly tunable nonlinear response of Au@WS2 hybrids with plasmon resonance and anti-Stokes effect

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Article information


Submitted
09 Dec 2018
Accepted
31 Mar 2019
First published
01 Apr 2019

Nanoscale, 2019,11, 8538-8545
Article type
Paper

Highly tunable nonlinear response of Au@WS2 hybrids with plasmon resonance and anti-Stokes effect

Y. Qiu, K. Chen, S. Ding, F. Nan, Y. Lin, J. Ma, Z. Hao, L. Zhou and Q. Wang, Nanoscale, 2019, 11, 8538 DOI: 10.1039/C8NR09946D

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