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Graphene–silicon phase modulators with gigahertz bandwidth


The modulator is a key component in optical communications. Several graphene-based amplitude modulators have been reported based on electro-absorption. However, graphene phase modulators (GPMs) are necessary for functions such as applying complex modulation formats or making switches or phased arrays. Here, we present a 10 Gb s–1 GPM integrated in a Mach–Zehnder interferometer configuration. This is a compact device based on a graphene-insulator–silicon capacitor, with a phase-shifter length of 300 μm and extinction ratio of 35 dB. The GPM has a modulation efficiency of 0.28 V cm at 1,550 nm. It has 5 GHz electro-optical bandwidth and operates at 10 Gb s–1 with 2 V peak-to-peak driving voltage in a push–pull configuration for binary transmission of a non-return-to-zero data stream over 50 km of single-mode fibre. This device is the key building block for graphene-based integrated photonics, enabling compact and energy-efficient hybrid graphene–silicon modulators for telecom, datacom and other applications.

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Fig. 1: Device.
Fig. 2: Raman characterization.
Fig. 3: Static electro-optical characterization.
Fig. 4: Dynamic characterization.
Fig. 5: Transmission measurements.


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The authors acknowledge funding from the European Union Graphene Flagship Project, ERC Grant Hetero2D and EPSRC grant nos. EP/509 K01711X/1, EP/K017144/1, EP/N010345/1, EP/M507799/5101 and EP/L016087/1. The authors also acknowledge Graphenea for the provision of CVD graphene samples.

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All authors conceived the phase modulator within the Graphene Flagship project. V.S., M.M., G.C. and M.R. carried out device design and testing. I.A., J.V.C. and C.H. fabricated the device. I.G., A.K.O. and A.C.F. performed material characterization.

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Correspondence to M. Romagnoli.

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Sorianello, V., Midrio, M., Contestabile, G. et al. Graphene–silicon phase modulators with gigahertz bandwidth. Nature Photon 12, 40–44 (2018).

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