Silicon-Organic Hybrid (SOH) Mach–Zehnder Modulators (MZM) for Single-Carrier IM/DD Line Rates of 500 Gbit/s and Beyond

Compact high-speed electro-optic modulators are key to next-generation optical transceivers for exa-scale data centers and large-scale artificial-intelligence (AI) clusters. As key performance metrics, the devices must combine large modulation bandwidth and low optical loss with compactness and low-voltage operation, while being amenable to efficient mass production, ideally on the silicon photonic platform. In this paper, we demonstrate silicon-organic hybrid (SOH) Mach-Zehnder modulators (MZM) that offer line rates in excess of 500 Gbit/s via low-complexity intensity-modulation-and-direct-detection (IM/DD) schemes. With π-voltage-length products UπL of only 0.67 Vmm, our devices combine efficiency and compactness, while being amenable to monolithic co-integration with a rich portfolio of proven silicon photonic devices. In a series proof-of-concept experiments, we demonstrate an SOH MZM with 280 μm-long phase-shifter sections, offering a 3-dB bandwidth of 74 GHz and a 6-dB bandwidth beyond 110 GHz along with a sub-1 dB phase-shifter loss. We achieve a PAM4 symbol rate of 204 GBd (line rate of 408 Gbit/s) and a PAM8 symbol rate of 176 GBd (line rate of 528 Gbit/s) – record values for MZM on the silicon photonic platform. We believe that our devices offer a highly attractive route towards next-generation optical transceivers with unprecedented efficiency and scalability.