Developing co-integrated photonics and electronics for faster and more efficient data centers
Salim Abdi defended his PhD thesis at the Department of Electrical Engineering on June 4th.
In his PhD research, focuses on integrating photonic and electronic chips vertically into a single compact system, using a method called wafer-scale bonding. This involves stacking two types of chips on top of each other at the wafer level: one with photonic signals and one with electronic signals. The materials that are used for this are based on indium phosphide (InP), which is known for its excellent performance in both optics and electronics.
Bonding technique
To make this integration work reliably and at scale, several technical challenges need to be overcome. For example, a special glue-like material called BCB is used to bond the layers together and ensure a strong, uniform and detect-free bond. Salim Abdi presents a new bonding technique in his thesis that takes advantage of the reflow properties of BCB while maintaining the exact alignment needed for the system to function. Another focus of his research is understanding and correcting the tiny distortions that occur during bonding, which could otherwise affect the fabrication accuracy of these delicate structures. These distortions were measured and compensated for, enabling precise manufacturing processes to continue.
Thermal management
Another challenge that needs to be taken into consideration for this integration is thermal management. Chips generate a lot of heat, which can reduce performance. Salim Abdi demonstrates a way to dissipate heat by using specially designed thermal ‘shunts’, which connect the hottest parts of the chip directly to a cooled base. These improvements lead to better-performing lasers, amplifiers, and photodetectors—all crucial building blocks for fast optical communication.
Electronic-photonic circuit
Finally, Salim Abdi showcases a co-designed electronic-photonic circuit that integrates high-speed photodetectors with electronic drivers on the same chip stack. This marks a critical step toward practical, scalable, and energy-efficient photonic-electronic systems that can be used for future data centers.
Title of PhD thesis: . Supervisors: Prof. Kevin Williams and Dr. Yuqing Jiao.