High-Speed Integrated Waveguide Photodiodes for Next-Generation Optical Communications

With applications such as cloud computing, social networks, and search, and the coming age of artificial intelligence and the Internet of Things (IoT), data usage is nearly doubling yearly worldwide and current data centers are facing enormous pressure to increase bandwidth and data transmission capacity. Although there have been numerous technological advances in optical communication systems that mitigate pressure on data links, it is predicted that current optical network architectures will not be able to keep up with the rising demand on bandwidth in the near future.
Furthermore, today's computers are not able to process information at the same rate as the rapidly rising demand of data, as the electrical interconnects between memory and processor nodes act as a bottleneck for efficient data transmission. Thus, we need a radical change in technology to fundamentally change the way that our data centers and high-performance computers operate in order to keep up with the ever-increasing data consumption in our society.
A promising solution to this issue is to use integrated photonics to create high-speed, low-power optical transceivers. Moreover, with the emergence of silicon photonics, photonics can be integrated onto the same chip as CMOS electronics to provide high-bandwidth optical interconnects between the CPU and memory units within a high-performance computer. In this work, I demonstrate high-speed integrated waveguide photodiodes for next-generation optical communications in future data centers and supercomputers.
More specifically, I designed and fabricated a 2 μm waveguide integrated photodiode, based on multiple InGaAs/GaAsSb type-II quantum wells, with dark current as low as 1 nA at −1 V, internal responsivity of 0.84 A/W and bandwidth >10 GHz at 2 μm. I also demonstrate ultra-low capacitance MUTC photodiodes on InP with a 44 GHz bandwidth-efficiency product (BEP). And, lastly, I report on the first quantum dot photodiodes heterogeneously integrated on silicon with a record low dark current (0.01 nA), record high 3-dB bandwidth (15 GHz), and a gain-bandwidth product of 240 GHz.