RF and Thermal Considerations of a Flip-Chip Integrated 40+ Gb/s Silicon Photonic Electro-Optic Transmitter

We demonstrate a flip-chip integrated electro-optic transmitter incorporating a high-swing CMOS driver and silicon photonic Mach-Zehnder modulator, and discuss the RF and thermal characteristics of the assembly. The transmitter showed a dynamic extinction ratio of 8 dB, which is the highest to date for 40+ Gb/s-class transmitters using CMOS drivers with silicon modulators. The input reflection coefficient of the module was mostly determined by the input electrical lines, solder bumps, and driver, while the electro-optic transfer function was mostly set by the Mach-Zehnder modulator. Despite the high power consumption of the driver and modulator (553 mW) and the close proximity between the electronic and photonic dies, the thermal simulations show that heat can be efficiently sunk from the bottom side of the silicon photonic die.