Insights Into Silicon Photonics Mach–Zehnder-Based Optical Transmitter Architectures

Mach–Zehnder-based modulator architectures lend themselves to the realization of high-data-rate Silicon Photonics transmitters. In this work the challenges set by the integration of such devices on silicon are analyzed in depth. The two main alternative electronic driver architectures, namely multistage and travelling wave, are compared with focus to power efficiency. This is, in fact, a key parameter when considering the stringent requirements of standard module form factors. A 25 Gbps multistage and a 56 Gbps travelling wave modulator have been realized. Each electro-optical transmitter is obtained by the 3D assembly of an electronic IC on top of a photonic IC through copper pillars. STMicroelectronics PIC25G Silicon Photonics platform has been adopted for the fabrication of optical devices, while 65 nm CMOS and 55 nm BiCMOS technologies are exploited to realize the electronic drivers. A 30% better power efficiency compared to Silicon Photonics state-of-the-art at similar data rates and comparable extinction ratio performance has been demonstrated in both cases. Since packaging is also a crucial aspect for Silicon Photonics high volume production, experiments on bare dice as well as on packaged chips are reported.