THz-to-optical conversion in wireless communications using an ultra-broadband plasmonic modulator

Future wireless communication networks will need to handle data rates of tens or even hundreds of Gbit s(-1) perlink, requiring carrier frequencies in the unallocated THz spectrum(1,2). In this context, seamless integration of THz links into existing fibre-optic infrastructures(3) is of great importance to complement the inherent portability and flexibility advantages of wireless networks and the reliable and virtually unlimited capacity of optical transmission systems. On the technological level, this requires novel device and signal processing concepts for direct conversion of data streams between the THz and optical domains. Here, we demonstrate a THz link that is seamlessly integrated into a fibre-optic network using direct THz-to-optical (T/O) conversion at the wireless receiver. We exploit an ultra-broadband silicon-plasmonic modulator having a 3dB bandwidth in excess of 0.36 THz for T/O conversion of a 50 Gbit s(-1) data stream that is transmitted on a 0.2885 THz carrier over a 16-m-long wireless link. Opticalto-THz (O/T) conversion at the wireless transmitter relies on photomixing in a uni-travelling-carrier photodiode.