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  • February 25, 2008 - Photonic crystals key to protective eyewear

    ECE researchers are using photonic crystals in special eyewear that may one day protect soldiers. A U of I research team is currently developing technology aimed to improve devices used to protect U.S. soldiers' eyes during combat. Even though the researchers have had much progress in the past two and a half years, they are continuing to make advances.

    "At this point, we've demonstrated the concepts in the lab that we theoretically predicted," said Brian Cunningham, an associate professor of electrical and computer engineering (ECE) at Illinois. "The biggest obstacle to overcome now has to do with making the response speed of the devices fast enough."

    The research project started shortly after Cunningham visited the U.S. Army Soldier System Center in Natick, Mass., a research laboratory headed by the U.S. Department of Defense that investigates and develops food, clothing, shelters, airdrop systems, and other service member support items for the U.S. military. While visiting the center in 2004, Cunningham gave a talk on photonic crystals, which are multilayer films used to control optical transmission, reflection, and refraction characteristics in biosensors.

    The presentation intrigued a program manager in charge of technological developments for the Army’s protective eyewear who was looking for a way to solve the Army's eye protection problem and believed that photonic crystal technology could be the solution, Cunningham said.

    Protective eyewear, which was first launched in the 1990s, is designed to protect U.S. soldiers from enemies attempting to disable them and United States lasers that are used when targeting. When they hit the eye, laser pulses can cause flash blindness, a visual impairment during and following exposure to a light flash of extremely high intensity, which can result in permanent blindness.

    "It is a concern for the soldier not only when they are there in the battlefield, but also for the rest of their lives," Cunningham said. "Because these weapons could be used against us, the U.S. Army wanted us to develop a technology that could counter them."

    The U.S. Army granted Cunningham and his research group, which consists of ECE graduate students Fuchyi Yang and Gary Yen, a contract to theoretically study potential concepts for a year. During that time, they designed devices and modeled them by computer. After the initial study, which took place from 2005 to 2006, the Army extended the grant for another two years, enabling the researchers to start building and testing hardware. They are currently one and a half years into the second stage.

    "We have electromagnetics simulation software that allows us to design the photonic crystal structure and incorporate all the shapes and sizes of the materials," Cunningham said. "In the computer, we can see how efficiently the device blocks light at different wavelengths and angles." While the eye protection devices currently available can rapidly react to laser radiation, they are heavy and expensive to make, Cunningham said. In addition, when certain wavelengths hit those devices, which are similar to sunglasses or goggles that cover eyes from all angles, they turn from clear to opaque, making it hard for the soldier to see out.

    "It's why (the Army) is interested in the photonic crystal technology," he said. "We can make devices that can reflect a specific band of wavelengths, but allow all the other wavelengths to come through so soldiers can still see."

    Cunningham said that parts of the research are highly classified, which poses some problems. While he has a security clearance for some information, he is unable to tell his graduate students who aid in the research any of the classified information. Therefore, Cunningham said that he, Yang, and Yen will most likely make incomplete devices and send them to the Army, so other researchers can add the additional materials.

    Contact: Brad Petersen, assistant director of communications, 217/244-6376.

    Writer: Bridget Maiellaro, ECE Illinois.