Shubhra Pasayat, the Dugald C. Jackson Assistant Professor in electrical and computer engineering at the University of Wisconsin-Madison, has earned a 2026 Defense Advanced Research Projects Agency (DARPA) Young Faculty Award.
The highly competitive DARPA Young Faculty Award program provides funding, mentoring and industry and national security contacts to researchers in junior faculty positions at academic and nonprofit research institutions across the United States. The goal is to develop the next generation of academic scientists, engineers and mathematicians whose long-term research focus has the potential to address national security needs.
Pasayat will build a new type of compact semiconductor-based laser diode that produces ultraviolet-c light, or UVC. UVC light is invisible to the naked eye and ranges between 100 and 280 nanometers, making it the most high-energy form of ultraviolet light.
The wavelength is special in other ways as well. UVC light from the sun interacts with ozone and oxygen in the earth’s atmosphere, preventing this spectrum of light from making it to the earth’s surface. That means there’s no naturally occurring UVC background interference, so the wavelength is especially valuable for sensing and communications applications. It’s also very efficient at damaging the DNA and RNA of various microbes, making it a powerful disinfectant for medical equipment and useful in water and air purification.
Currently, UVC light is produced by bulky, inefficient lamps that use fragile UVC bulbs. In her project, Pasayat plans to develop a much smaller, rugged and more energy-efficient UVC light source that could enable a whole new class of portable scanning and disinfecting devices.
The problem is that aluminum gallium nitride, the semiconductor material needed to produce these tiny laser diodes, is extremely sensitive to nanoscale defects. “A microscopic flaw can shut down the whole system,” explains Pasayat. “And the problem gets worse the harder you push; the more power you want from it, the more defect-sensitive the material becomes.”
To get around this issue, Pasayat has developed a design in which the diode keeps operating even if one piece fails. Key to the project is the Ultra-Wide Bandgap Semiconductor Metal-Organic Chemical Vapor Deposition (MOCVD) reactor installed in Pasayat’s lab in 2025. The machine uses high heat and pressure to fabricate high-quality samples of next-generation III-nitride semiconductor materials like aluminum gallium nitride. “We will use a set of techniques that we have already shown to work to make the material more efficiently and to make it cleaner,” she says. “That will help us get to the extremely high output power we have proposed for the laser.”
In fact, the project hinges on producing the highest quality layers of aluminum gallium nitride possible. There is one bottleneck: The characterization techniques used to measure and assess the material are not widely available. Currently, the UW-Madison College of Engineering and Department of Electrical and Computer Engineering are supporting the installation of a key material characterization instrument that will allow researchers to test these materials; this instrument will enable Pasayat to assess and tune her semiconductor materials and continue to move the project forward.
Pasayat says this project brings together all the research her lab has undertaken over the last few years, including work on UV-A lasers as well as advanced semiconductor device fabrication development leveraging the WCNT facilities. “Each of these has been a separate thread, and this project is where they all come together in one ambitious device, which makes it a centerpiece for the lab,” she says.
By the end of this three-year project, Pasayat hopes to produce a UVC laser diode several times more powerful than anything else previously demonstrated. “But success is also proving the ideas that are underlined in our proposal,” she says. “If we can show that this new design really does make a device more durable and functional in extreme environments, and that our technique works in this demanding material, then we will have built up a foundation that keeps us going long after this project ends.”
Disclaimer: This research will be developed with funding from the Defense Advanced Research Projects Agency (DARPA). The views, opinions and/or findings expressed are those of the authors and should not be interpreted as representing the official views or policies of DARPA or the U.S. Government.
Featured image caption: Shubhra Pasayat, center, will use her DARPA Young Investigator Award to develop a semiconductor-based laser diode that produces ultraviolet-c light. Credit: Todd Brown.