Explorer of Light
When people discover that Sharon Weiss works in optics, they often ask if she can fix their glasses.
“I say, ‘No, but I can tell you how they work,’” says Weiss of her field of optics — the study of light, not eyewear. “Light can carry energy and information, something as simple as voice or music or as complicated as video.” Yet the research into optics conducted by Weiss, assistant professor of electrical engineering, is anything but simple.
In fact, research conducted in her Vanderbilt University School of Engineering labs — as well as in collaborations across campus — has the potential to revolutionize the next generation of computers, military safety, health care and even museum lighting. The Weiss Group focuses on research involving photonics, optoelectronics, nanoscience and technology, and optical properties of materials. Its research initiatives are supported in part by the National Science Foundation and several Department of Defense agencies.
Photonics concerns the controlled flow of photons, or light particles, and is the optical equivalent of electronics. The field covers a huge range of science and technology applications, including optical computing, laser manufacturing, biological and chemical sensing, display technology and medical diagnostics and therapy. Weiss’ expertise in photonics has made her a frequent research collaborator across the university.
Sharing Optics Expertise
“Sharon contributes to the collaborative atmosphere in two ways,” says Sandra Rosenthal, director of Vanderbilt Institute of Nanoscale Science and Engineering. “First, her science fills a niche that complements other efforts under way at Vanderbilt. For example, her expertise in optics can be utilized to develop biosensors and logic components for photonic communications, or to enhance absorption in a novel solar cell. She has core expertise that benefits many programs.
“Secondly, she has a personality well-suited to collaboration. Not everybody is a good collaboration partner,” says Rosenthal, who is also professor of chemistry, physics, pharmacology and chemical and biomolecular engineering. “Sharon can work just as well as a member of a team as she works individually. She’s engaged, prompt, responsible and does her fair share.”
Their collaboration began shortly after Weiss came to Vanderbilt, when Rosenthal was doing research with solid-state lighting devices, which use light-emitting diodes (LEDs) instead of electric filaments for illumination. “It turned out that Sharon had covered this material in a course she had at the Institute of Optics while she was a graduate student,” Rosenthal says. “I asked her if she wanted to form a partnership in the research going forward and was delighted when she said yes.”
Weiss and Rosenthal explore LED lighting improvements using ultrasmall cadmium selenide nanocrystals. Their research has focused on the development of white LEDs, which have the potential for higher efficiency and longer lifetimes compared to other current lighting technologies. The ultrasmall nanocrystals emit pure white light with superior color quality, which is especially important for applications like museum lighting.
Computing at the Speed of Light
Weiss and Richard Haglund, professor of physics, recently launched a project exploring the uses of light in computing.
“The demand for faster computational speed is no longer being met by faster processors,” Weiss explains. “Computers have been getting faster and faster, but now you will often find dual core or quad core processors to accomplish that. The processing speed of each core is no longer getting much faster. There has to be some revolution in computing, and one of the viable options is to do it with light.”
“Her science fills a niche that complements other efforts under way at Vanderbilt.”
Director, Vanderbilt Institute of Nanoscale Science and Engineering
Currently, computer cores include chips made from silicon, but there are scaling limits with the present approach of increasing speed by shrinking the size of silicon transistors. “The industry wants to stay with silicon as long as possible,” she explains. “Billions of dollars have been invested in capital equipment.”
Weiss and Haglund’s research explores whether integrating vanadium dioxide with silicon might deliver increases in speed without the costly move away from the silicon infrastructure. “The path is set; it’s just a matter of time,” Weiss says. “I would not be surprised within 10 years to see a significant number of optical components in computers.”
Building on the Foundation
Silicon and its derivatives were the foundation of Weiss’ doctoral thesis at the University of Rochester and remain central to her research. Silicon is traditionally known as the material of choice for electronic applications. The integrated circuits that control computers and cell phones, for example, are primarily made out of silicon. “Silicon is a relatively abundant material and it is the backbone of most modern technology,” she explains. “My Ph.D. adviser used to say, ‘If it can be done in silicon, it must be done in silicon.’” Many of Weiss’ research initiatives examine the potential of silicon for applications that involve light instead of electricity.
In her lab, Weiss and her team of eight graduate and four undergraduate students work on optical research initiatives. Several projects take advantage of the large surface area that can be obtained by introducing nanoscale holes into silicon, forming a material called porous silicon. When coated with appropriate chemicals, the tiny holes — more than ten million times smaller than one meter — can be used to selectively capture specific biological molecules of interest. Light interaction with the molecules in the holes enables identification and quantification of the molecules. The research opens up the possibility of performing cost-effective environmental monitoring or medical diagnostics in real time on a very small scale.
“Combining new innovations in nanotechnology with existing knowledge about how to capture molecules on microscope slides has already enabled significant breakthroughs in disease detection and treatment,” Weiss says.
Weiss is also collaborating with Paul Laibinis, professor of chemical and biomolecular engineering, to synthesize DNA inside porous silicon. “You can think about DNA as your genetic makeup. What we are doing is putting a particular sequence of DNA inside our porous silicon biosensors,” she says. “If geneti-cists know that the presence of a particular DNA sequence in one section of a person’s genetic code means that person is more likely to develop cancer or heart disease, then we can identify if that sequence is present by comparing it to the complementary DNA sequence that we can synthesize in our porous silicon sensors.”
Why Vanderbilt School of Engineering
When it came time to apply for her first faculty position after getting her doctorate, the New York state native initially did not consider moving too far south. Her ties to Rochester were strong; she had grown up there and had been recruited by the University of Rochester to play soccer for four years. She attended the university and its Institute of Optics from freshman year through earning her doctorate.
“Vanderbilt is the kind of place where you don’t just pay lip service to collaborative research.”
Dennis Hall, former director of Rochester’s Institute of Optics, had become Vanderbilt’s vice provost for research and dean of the Graduate School. He suggested Weiss take a look at Vanderbilt. Drawn by the “engaging interdisciplinary climate,” she joined the Vanderbilt School of Engineering in 2005.
“The research that I do is not traditional engineering. Van-derbilt is the kind of place where you don’t just pay lip service to collaborative research,” she says. “I also sensed Vanderbilt had an upward slope. … it was going somewhere fast.”
Honored by the President
Weiss also is going somewhere fast. In 2009, she was one of 100 young researchers recognized by President Barack Obama with a Presidential Early Career Award for Scientists and Engineers (PECASE). The award is the highest honor bestowed by the federal government on young engineers. That led to an invitation to attend the German-American Frontiers in Science symposium this summer. Only 70 researchers under the age of 45 were invited. “They have speakers who talk about timely research topics that span multiple disciplines, followed by lots of time for discussion,” Weiss says. “Bringing people together who individually have great ideas and asking them to think about current challenges in crosscutting fields suggests that more ideas will be generated and potential solutions found.” Weiss has also been selected to attend the National Academy of Engineering-sponsored U.S. Frontiers of Engineering symposium this fall.
She’s still as enthusiastic about the field of optics as when she was a college freshman taking an introduction to optics class, and readily elicits the same passion in engineering students. In teaching a course on signal processing and communication, she adapted the syllabus to include a section on fiber optics, which allows students to understand how sound, pictures and data can be transferred for phones, television and Internet usage.
Weiss often includes laboratory exercises in each course curriculum to reinforce concepts with hands-on activities. “If you talk in abstract equations, students often just memorize what they need to and forget it soon after the exam,” she says. Weiss is also active in community outreach as she participates in a number of programs such as TWISTER (Tennessee Women in Science, Technology, Engineering and Research) at Nashville’s Adventure Science Center.
Knowledge is something she believes in giving not just to her students but also using to stretch herself. “Research and teaching are a rewarding balance. With research, you can put in a lot of time and sometimes you get few tangible rewards. Other times you put in a little effort and get a lot out,” she says. “With the classroom, it’s almost immediate impact. It’s immediate gratification that you’re making a difference.”