Comparison of Back and Top Gating Schemes with Tunable Graphene Fractal Metasurfaces

In this work, fractal metasurfaces that consist of periodic gold squares on graphene are used to increase light–graphene interaction. We show by simulations and experiments that higher level fractal structures result in higher spectral tunability of resonance wavelength. This is explained by higher field localization for higher level fractal structures. Furthermore, spectral tunability of fractal metasurfaces integrated with graphene is investigated comparing two different schemes for electrostatic gating. Experiment results show that a top-gated device yields more spectral tunability (8% of resonance wavelength) while requiring much smaller gate voltages compared to the back-gated device.