108 Gbit/s Plasmonic Mach–Zehnder Modulator with > 70-GHz Electrical Bandwidth

We report on high-extinction-ratio, ultrafast plasmonic Mach-Zehnder modulators. We demonstrate data modulation at line rates up to 72 Gbit/s (BPSK) and 108 Gbit/s (4-ASK). The driving voltages are U
_d
= 4 and 2.5 V
_p
for 12.5 and 25 μm short devices, respectively. The frequency response shows no bandwidth limitations up to 70 GHz. Static characterizations indicate extinction ratios > 25 dB.