All-plasmonic Mach–Zehnder modulator enabling optical high-speed communication at the microscale

The authors demonstrate a 70 GHz modulator in a 10-μm-long two-dimensionally localized gap-plasmon waveguide system. Optical modulators encode electrical signals to the optical domain and thus constitute a key element in high-capacity communication links 1 , 2 . Ideally, they should feature operation at the highest speed with the least power consumption on the smallest footprint, and at low cost 3 . Unfortunately, current technologies fall short of these criteria 4 . Recently, plasmonics has emerged as a solution offering compact and fast devices 5 , 6 , 7 . Yet, practical implementations have turned out to be rather elusive. Here, we introduce a 70 GHz all-plasmonic Mach–Zehnder modulator that fits into a silicon waveguide of 10 μm length. This dramatic reduction in size by more than two orders of magnitude compared with photonic Mach–Zehnder modulators results in a low energy consumption of 25 fJ per bit up to the highest speeds. The technology suggests a cheap co-integration with electronics.