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THz spectroscopy of graphene complementary split ring resonators

Suzuki, Satoru (NTT Basic Research Labs., Atsugi, JPN); Yamamoto, Hideki (NTT Basic Research Labs., Atsugi, JPN)

Split ring resonators are used as a fundamental constituent of metamaterial to obtain negative permeability. Several simulation studies have shown that plasmonic split ring resonators consisting of graphene have excellent performance in the THz region, owing to the relatively long life time of plasmons in graphene [1-3]. In the THz region, the light-graphene interaction is dominated by intraband transition, and absorption can easily exceed the universal absorption of 2.3 %/layer caused by interband transition [4]. Moreover, the optical properties of a graphene split ring resonator, such as the resonance frequency, can be tuned by gate voltage, which can not be achieved in a conventional metal split ring resonator. Nevertheless, to the best of our knowledge, no experiments on graphene split ring resonators have been reported. We fabricated complementary split ring resonators by patterning doublelayer graphene grown on a SiC substrate. In the complementary split ring resonator device, the graphene layer has a continuous form. Thus, we can expect that the Fermi level of the entire graphene layer, and thus, the resonance frequency of the device, can be tuned by using an ion liquid- or ion gel-based gating method [5]. The devices showed resonances at about 2.5 and 6.5 THz for x- and y-polarized light, and the absorption was estimated to be about 3 and 6 % at the resonance frequencies, which are comparable or even larger than the interband absorption. The experimentally observed spectra were fairly consistent with simulations. These results show the possibility of graphene-based configurable metamaterials. This work was partly supported by JSPS KAKENHI.

[1] J. Wang et al., J. Phys. D: Appl. Phys. 47, 325102 (2014).

[2] Y. Fan et al., Opt. Lett. 38, 5410 (2013).

[3] N. Shen, Phys. Rev. B90, 115437 (2014). [

4] S. Suzuki et al., Proc. MNC2015 (Jpn. J.Appl. Phys.), in press.

[5] H. Yan et al., Nature Nanotechnol. 7, 330 (2012).

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