Optical bumps for pick and place optics
Lead student: Drew Weninger
The goal is to invent methods for coupling light between two separate chips (or a chip and an interposer, an interposer and an interposer, a chip and a board, etc.) and between two layers of the same chip. In other words, this project focuses on getting light to move up, down, and between chips with low loss, high alignment tolerance, and simple fabrication steps. Undergoing this type of inventive process requires working with difficult materials systems such as fabrication of silicon, silicon nitride, and silicon oxynitride waveguides using glass substrates and complex manufacturing systems including high speed pick and place die bonding tools.
Shown: visible light being edge coupled into a silicon nitride waveguide on a glass substrate.
Low Temperature Ge-on-Si Photodetectors
Lead student: Stephanie Marzen
Electronic-photonic integration in Si CMOS circuits should be done in the most flexible manner possible, and low temperature processing of Ge on Si, < 450C allows photodetectors to be incorporated anywhere amongst the metal interconnects. We optimize the growth methods for semiconductors on amorphous substrates, grow high quality Ge epitaxy on Si, and engineer defect reduction by annealing at low temperatures. We also fabricate photodetectors from these materials to demonstrate highly efficient light detection with low dark current.
Picture coming soon! 🙂
Broadband dFT spectrometry
Lead student: Maarten Robbert Anton Peters
We’re designing a on-chip broadband (1.2-1.7 um) spectrometer. Our digital Fourier Transform spectrometer, consists of a Mach-Zehnder Interferometer (MZI) with cascaded optical switches in both arms. Using the switches, the optical pathlength in each arm can be changed. Each perturbation gives a unique optical pathlength difference between the two arms. With a single detector, measuring the output intensity of the MZI as a function of the pathlength difference, the input spectrum can be reconstructed. The use of a single detector allows for a superior signal-to-noise ratio compared to dispersive on-chip spectrometers.
Shown: layout of a 64 channel dFt spectrometer designed by former student Derek Kita
Novel methods for training the U.S. manufacturing workforce
Lead student: Drew Weninger
Here, it is all about training people to do complicated tasks as quickly as possible. In the semiconductor manufacturing sector, which includes optical technicians, time is absolutely critical – the precious seconds it takes for a wafer to have new metals deposited on it or be etched by gasses or acids adds up when there are hundreds of process steps each requiring complex tools. Those tools need to be properly operated, maintained, updated, and fixed, and the time it takes to do so can become a bottleneck to throughput. For example, this played an important role in the chip shortage issues of 2020. We use novel methods like virtual reality simulations and bootcamps which give technicians hands on experience with complex manufacturing tools in order to reduce the time it takes to train workers from days to hours and hours to minutes. Every second counts.
Shown: PCB with photonic and electronic components designed by MIT instructors and built during our photonics bootcamps by future optical technicians.