The field of optics (the interaction of light and matter) is playing an increasingly important role in electrical engineering. Steve Blair, an associate professor of electrical and computer engineering, uses novel optical techniques in many areas of his research.
One project involves intensifying the effects of light to make information transmission more efficient. Dr. Blair and his associates are working with “slow light” to achieve these effects. Light is transmitted through a path consisting of tiny resonators that draw light in as it moves along a waveguide. Some of the light couples into the resonator and circulates, while the rest bypasses the resonator. Light that gets trapped and then released from the resonator comes out at a later time and is, in effect, “slowed down.”
As optical communication technologies become more prevalent, slow light research may have important applications. Slowing light down increases its intensity, allowing more efficient sensing and nonlinear effects on an optical microchip. These effects can be used in low power optical sensor networks or to perform optical signal processing operations that enable more efficient transmission of information through optical networks.
Dr. Blair is also observing the nonlinear effects of light in nanodevices (about a thousandth of a human hair in diameter). “We use optical antennas that allow us to manipulate light at the nanoscale level,” he says. “Our goal is to see what sort of sensing and nonlinear effects we can observe and whether we can make useful nanophotonic devices from this research.”
As light comes into contact with the tiny antennas, it is focused into feedgaps that are smaller than the wavelength of light. Focusing light to a point effectively slows it down-much like the resonator does-and strengthens the light signal, allowing for the observation of nonlinear effects such as the generation of light at twice the original frequency.
Dr. Blair and his team also immobilize individual molecules of DNA or proteins in the feedgaps to observe what effect the intensified light has on the molecules. Called single-molecule spectroscopy, the research may show whether each molecule can be accurately identified-something that historically has been difficult to do with individual molecules.
“If we are observing many molecules, then it is easier to detect and identify them,” Dr. Blair says. “But looking at only one molecule, detection is the easy part. Identification is the hard part.”
Dr. Blair is taking the identification strategy even further by trying to improve microarray tools for medical research and, eventually, clinical diagnostics. Microarrays are glass slides affixed with thousands to millions of spots of single-stranded DNA sequences. When a sample solution is introduced, the complementary strands of DNA in the solution, which are fluorescently labeled, bind to the appropriate spots on the microarray and form a duplex. The array is then scanned with an optical beam and fluorescence emission is collected at each spot. Based on how the spots light up, the investigator can identify how much of a particular DNA sequence was in the solution.
While microarrays are common tools in medical research, they are used only in very limited circumstances in clinical diagnostics. One of the big barriers to using microarrays is reliability. While many dispute how much of the data obtained from a microarray is accurate, some would say that perhaps only 60 percent of the information can reliably be used. “A lot of data is being thrown away that could otherwise be used,” says Dr. Blair. “Moreover, in a clinical setting where it may be a matter of life or death, you’ve got to get it right.” Knowing that the information obtained from a microarray is not perfect, Dr. Blair is developing methods that may improve the reliability so that more of the data can be used.
“We’re working with collaborators to test the limits of what can be done,” Dr. Blair says. “With our modeling and experimental techniques, the end result will be that we can provide answers with a higher level of confidence than we currently see.”
Although practitioners are looking for the next big technological advance, such as next-generation sequencing, Dr. Blair thinks there is still much room for improvement with microarray technology. “There is a huge installed base,” he says. “And it’s still a dominant technology among the research community.”
For more information, please visit the Photonics Research Group web page.
Learn more about Dr. Steven Blair.