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Accepted: Apr. 18, 2019

Posted: Jul. 8, 2019

Published Online: Jul. 8, 2019

The Author Email: Guangqing Du (guangqingdu@mail.xjtu.edu.cn), Feng Chen (chenfeng@mail.xjtu.edu.cn)

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Yanhong Dong, Qing Yang, Guangqing Du, Feng Chen, Noor Uddin, Dayantha Lankanath, Xun Hou. Electronic manipulation of near-field nanofocusing in few-layer graphene-based hybrid nanotips[J]. Chinese Optics Letters, 2019, 17(7): 072501

Fig. 1. Schematic of the simulated FLG-based nanotip hybrid system. The graphene-coated Au tip is modeled as a conical taper terminated by a hemisphere of radius $R$ as its point and elevated a distance $d$ above a $SiO2$–graphene–$SiO2$ substrate. An electromagnetic plane wave is incident at an angle $θ$ with respect to the surface normal. A 300-nm-thick perfectly matched layer (PML) encloses the simulation domain.

Fig. 2. Cross-section of mono-graphene-based nanotip structure. Calculated images of the e-field distributions in the case of mono-graphene in the substrate (The curvature radius of the nanotip is $R=30 nm$. The vertical spacing between the nanotip and substrate is $d=20 nm$, and incident light travels along the $X$ direction).
Fig. 3. Permittivity of MLG with respect to different Fermi energies. (a) The red, blue, black, green, and orange lines are corresponding to 0.1, 0.2, 0.3, 0.4, and 0.5 eV, respectively. (b) The normalized e-field enhancement and resonant frequency of the nanotip hybrid system depending on the Fermi energy of excited graphene. (c) Real and (d) imaginary parts of graphene permittivity with respect to the layers of FLG changing from 1 to 5 ($EF$ is biased to 0.5 eV).