Research
We are at the Max Planck Institute for Microstructure Physics in Halle, Germany in the Department of Nanophotonics, Integration, and Neural Technology (NINT) and the Department of Electrical & Computer Engineering at the University of Toronto.
Our research aims to create the devices and microsystems for future computers. Computers are not only our desktops and laptops. They can also be very large-scale systems like datacenters, or be very portable like phones and watches. Computers augment our abilities to analyze and will continue to be important to help us understand and solve the toughest problems facing humanity, such as the climate, health, and sustainability. How will computers be like 10 years from now?
In large-scale systems, there is a great need to reduce the power consumption and latency of computing for machine learning and artificial intelligence applications. Computing paradigms that fundamentally go beyond digital electronics, like quantum computing and neuromorphic computing, are on the horizon. In terms of portable devices, people are becoming increasingly close and attached to computers. The next types of computing devices will need to have interfaces that are more comfortable, convenient, and functional than phones and watches. In the distant future, could a computer be even integrated within a person?
Motivated by the needs of future computers, our main research topics are visible light integrated photonics, neurotechnology, and neuromorphic devices and circuits. Within U of Toronto, we have a project on hybrid InP-on-Si integrated photonics for data communications.
Visible Light Integrated Photonics on Silicon
The field of silicon (Si) photonics aims to form photonic devices and circuits on Si substrates using the manufacturing infrastructure of CMOS electronics. The large Si substrates and wafer-scale microelectronic packaging lead to high production volumes that can reduce the cost of an optical chip. Si photonics is transforming data communications, which use infrared wavelengths near 1310nm or 1550nm.
We are working to create integrated photonic platforms on Si that operate in the visible wavelength range (between 450nm to 650nm). The visible spectrum open numerous applications for integrated photonics, including micro-displays, quantum information, and sensing. Silicon nitride waveguides with broadband transparency can be realized on Si substrates. However, many challenges abound, such as feature size limitations, material absorption, and active device (lasers and modulators) integration. Many innovations are needed to realize highly functional visible light integrated photonic platforms.
Integrated Neurophotonics and Neurotechnology
We are bringing our expertise in foundry integrated photonics to create new technologies, such as implantable probes, recording arrays, and miniature microscopes, to study the brain. Much remains unknown about the complex and dense connectivity among the neurons in the brain. Developments in optogenetics, optical indicators, and multiphoton imaging are revolutionizing how light is used to study neural connectivity. Taking advantage of wafer-scale integration, our technologies will enable functionality that cannot be achieved with free-space or fiber optics, and will enable high density recording/stimulation in multiple modalities. These technologies are new tools for the neuroscience community and serve as new types interfaces to the brain.
Integrated neurophotonic probes for light-sheet microscopy and beam-steered optogenetic stimulation
Vanadium Dioxide Neuromorphic Devices and Circuits
Vanadium dioxide (VO2) exhibits a reversible insulator-metal transition (IMT) that can be initiated thermally (near 67oC), by carrier injection, or optically. In the intermediary state between the insulator and metallic phases, VO2 can generate electrical oscillations. We have recently discovered that VO2 microwires can serve as non-volatile memory at room temperature. The oscillatory and memory properties of VO2 can enable new types of devices for neuromorphic computing.
VO2 photo-electric memory and oscillator (submitted)
Hybrid InP-on-Si Photonics (U of T-only project)
Fiber optic communications can reduce the power consumption and latency in the communication within and between datacenters and are essential for broadband connectivity. Si photonics is a good candidate to serve high-volume markets due to the large Si wafer sizes, integration density, and mature manufacturing.
To integrate lasers onto Si photonic platforms for the infrared spectrum, an approach is to bond InP-based optically amplifying materials onto the top surface of a Si photonic wafer. In collaboration with SCINTIL Photonics, we are working on hybrid InP-on-Si integration where the InP is bonded from the backside of the wafer, onto the buried oxide (BOX) layer. Backside bonding enables hybrid laser integration onto multilayer Si photonic platforms and significantly improved wafer-scale uniformity in the oxide spacer thickness which should improve device yield.
