O-Band Silicon Ring Modulators With Highly Efficient Electro- and Thermo-Optic Modulation

As future computing systems increasingly demand higher bandwidth and energy efficiency, the development of faster and more efficient modulators is becoming a critical component of optical transceivers. In this paper, we present O-band silicon ring modulators (RMs) which are highly optimized in terms of electro- and thermo-optic modulations for an energy efficient optical I/O link. A highly optimized vertical p-n junction design is used to enhance the electro-optic efficiency, and fabricated RMs have 2 dB better transmitter penalty and bandwidth trade-off than previously reported lateral p-n junction based RMs. To improve the thermo-optic efficiency, Si substrate undercut (UCUT) process module is introduced. The efficiency increases more than 2.7 times with UCUT as 106-GHz/mW (0.608 nm/mW) with 5 μm radius RM, and no performance degradation is observed with 50-Gb/s NRZ operation.