A sub-pJ/bit, low-ER Mach-Zehnder-based Transmitter for chip-to-chip Optical Interconnects

Designing high-speed and low-power interconnects is a challenge for high performance computing applications, while silicon photonics can provide attractive solutions to perform high-density communications. This paper presents an electro-optic transmitter operating at 20 Gbps (gigabit per second), as a first step toward the demonstration of chip-to-chip optical links. The architecture is based on a dual-drive Mach-Zehnder interferometer co-integrated with a 55-nm CMOS driver. Design optimizations and trade-offs analysis enable low-energy and negligible bit error rate ( $BER ) transmission at 20 Gbps, by exploring a firstly reported low extinction ratio (ER) modulator. A wire-bonding board assembly is then carried out to co-integrate hybrid transmitter. Co-simulations are presented and show good agreement with experiments. Combined with an adequate MZM bias, this solution achieves a minimal energy consumption of 0.9 pJ/bit while ensuring a sufficiently large ER of 0.73 dB for chip-to-chip interconnects applications.