SCIENCE CHINA Information Sciences, Volume 60, Issue 8: 082402(2017) https://doi.org/10.1007/s11432-016-0539-6

## Ultra-compact tunable graphene-based plasmonic multimode interference power splitter in mid infrared frequencies

• AcceptedDec 2, 2016
• PublishedFeb 20, 2017
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### Abstract

In this paper, we propose graphene-based plasmonic multimode interference power splitters with ultra-compact size working in mid infrared range. Further, the arbitrary-ratio 1$\times$2 power splitter with a size of 140 nm$\times$232 nm, where the splitting ratio can be tuned continuously from 1:1 to 100:0, is numerically demonstrated. Meanwhile, the graphene-based arbitrary-ratio 1$\times$2 power splitters with different frequencies and chemical potentials are also investigated. The proposed multimode interference structure with a deep nanoscale footprint might be a fundamental component of the future high density integrated plasmonic circuit or on-chip plasmonic interconnect techniques.

### Acknowledgment

The authors are grateful to the support by Natural Science Fund of China (Grant No. 61378058), Science and Technology Fund of Quanzhou (Grant No. Z1424009), Fujian Province Science Fund for Distinguished Young Scholars (Grant No. 2015J06015), Promotion Program for Young and Middle-Aged Teachers in Science and Technology Research of Huaqiao University (Grant No. ZQN-YX203) and Project for Cultivating Postgraduates' Innovative Ability in Scientific Research of Huaqiao University (Grant No. 1511301022).

• Figure 1

(Color online) (a) The schematic of 1$\times$2 power splitter; (b) the magnetic field ($H_{z}$) distribution of 1$\times$2 power splitter; (c) the normalized optical energy flux density distribution of 1$\times$2 power splitter, with an operation mid infrared frequency of 6e13 Hz (5 $\mu$m) and a chemical potential of 0.6 eV respectively. The width and length of ${\rm WG}_{\rm in}$ are 15 nm and 100 nm respectively, width and length of output waveguides of 1$\times$2 power splitter are 20 nm and 100 nm respectively. The perfect matched layers (PML) prevent the plasmonic field reflected back from the right end of the MMI waveguides.

• Figure 2

(Color online) (a) Schematic of 1$\times$2 power splitter with a rectangle removed; (b) and (c) are the corresponding $H_{z}$ distribution and the normalized optical energy flux density distribution with an operation mid infrared frequency of 6e13 Hz (5 $\mu$m) and a chemical potential of 0.6 eV, $L_{\rm r}$ = 10 nm, $W_{\rm r}$ = 20 nm. The other geometrical parameters are the same as structure shown in Figure 1(a).

• Figure 3

(Color online) The PSRs of 1$\times$2 power splitter at 6e13 Hz, $\mu_{\rm c}$ = 0.6 eV with the $W_{\rm r}$ being 20, 22 and 25 nm respectively.

• Figure 4

(Color online) (a) The PSRs of 1$\times$2 power splitter at $\mu_{\rm c}$ = 0.6 eV with operation frequencies of 5.6e13, 5.8e13 and 6e13 Hz (5.36, 5.17 and 5.00 $\mu$m) respectively; (b) the PSRs of 1$\times$2 power splitter at 6e13 Hz with chemical potentials of 0.6 and 0.7 eV respectively.

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