Graphene photodetectors for high-speed optical communications

Although silicon has dominated solid-state electronics for more than four decades, a variety of other materials are used in photonic devices to expand the wavelength range of operation and improve performance. For example, gallium-nitride based materials enable light emission at blue and ultraviolet wave-lengths(1), and high index contrast silicon-on-insulator facilitates ultradense photonic devices(2,3). Here, we report the first use of a photodetector based on graphene(4,5), a two-dimensional carbon material, in a 10 Gbit s(-1) optical data link. In this interdigitated metal-graphene-metal photodetector, an asymmetric metallization scheme is adopted to break the mirror symmetry of the internal electric-field profile in conventional graphene field-effect transistor channels(6-9), allowing for efficient photo-detection. A maximum external photoresponsivity of 6.1 mA W-1 is achieved at a wavelength of 1.55 mu m. Owing to the unique band structure of graphene(10,11) and extensive developments in graphene electronics(12,13) and wafer-scale synthesis(13), graphene-based integrated electronic-photonic circuits with an operational wavelength range spanning 300 nm to 6 mm (and possibly beyond) can be expected in the future.