Blazing Its Own Path Infrared technology at the Center for High Technology Materials' FAST Center is being developed for commercial applications. By Sherry Robinson   Infrared technology isn't exactly a household word but it should be. You use it to play your CDs. And some new camcorders can now shoot at night using a sensor that works in infrared. The military has used infrared devices since World War II to see in the dark. For both surveillance and countermeasures infrared is still a hot research area to the nation's defense agencies, and the same technology lends itself to commercial applications. Photo by Michael Mouchette New uses require new materials and minute devices. Kevin Malloy and his colleagues and students at the Center for High Technology Materials (CHTM) are doing just that with funding from the U.S. Air Force, the U.S. Army and U.S. Defense Advanced Research Projects Agency. Malloy, an associate professor of electrical engineering, is director of the FAST (Future Aerospace Science and Technology) Center for Infrared Surveillance and Countermeasures. A partnership with North Carolina A&T State University, the center is funded by the Air Force to promote minority education and support ongoing research in infrared sources and detectors. Malloy observes that UNM "probably has the world's best university program" in infrared countermeasures.   Kevin Malloy and colleagues at UNM's Center for High Technology Materials are working on new uses and materials for infrared devices. Photo by Michael Mouchette "We do a very good job of keeping to the spirit of the FAST centers," Malloy says. "We get a lot of very good minority undergraduate and graduate students, and they're very successful. We do very good technical work, which makes the Air Force happy." Infrared devices "see" by detecting the invisible color infrared in radiating heat from human bodies or the exhaust of a jet. They can also spot an object against the cold of deep space. Related research at the center includes countermeasures, used to fool infrared technology. Take heat-seeking missiles, for example. The intended target can drop flares or try to dodge the missile but both tactics are inefficient. What if a plane or tank could be invisible to the missile or use lasers to turn it off course or burn out its sensors? These detectors are also useful for pollution monitoring. Infrared's longer wavelengths penetrate smoke, moisture or airborne chemicals better than visible wavelengths, so the devices can identify pollutants at great distances. Another application of this technology is in fire fighting. These detectors are also useful for pollution monitoring. Infrared's longer wavelengths penetrate smoke, moisture or airborne chemicals better than visible wavelengths, so the devices can identify pollutants at great distances. Another application of this technology is in fire fighting. Kamil Agi, a former student of Malloy's, who is now a research engineer at CHTM, studied infrared cameras that allow firefighters to see through smoke and detect hotspots or fires behind doors or in walls. He saw a need for video transmission of infrared images, specifically between firefighters in a burning building and personnel in the truck. "A guy in a fire is nervous in all that heat," Agi says, and may not be thinking clearly. He developed technology that allows firefighters inside a building to be linked with personnel outside the building, so a fire chief can participate in decision-making. In October Agi formed K&A Wireless LLC to market his device and has already sold two. CHTM is well known for its laser research, and Malloy and his colleagues have done some of their best work in infrared lasers. The semiconductor laser is the laser of choice, he explains, because it's small, efficient and inexpensive. These lasers on a chip can send messages along a fiber-optic cable and gather sound from a compact disc but they can't yet produce signals at a wide range of different wavelengths. Presently they work only in a narrow band of the visible spectrum and the adjacent near-infrared wavelengths of about one micron. Scientists would like to have longer wavelengths available, from the mid-infrared to the end of the radio spectrum (2 to 100 microns) or be able to tune to different wavelengths. This would make point-to-point laser telecommunications possible and eliminate costly and cumbersome cables. The FAST center has successfully made such devices. Two research faculty - Ralph Dawson, a former distinguished technical staff member at Sandia National Laboratories, and Ron Kaspi, who also works with the Air Force Research Laboratory - have developed 2- and 4-micron semiconductor lasers that have defense and commercial applications. Although a half dozen other labs are doing similar work, Dawson says, "we're trying a different set of materials and material structures to make the output more intense." These lasers, which are smaller than a grain of salt, could some day remotely identify the composition of automobile exhaust, Dawson says. They could also be used to detect signs of aging in explosives without getting near them. And they could be used in pollution monitoring or to control industrial processes. "It's mostly pushed by military applications, but commercial applications are certainly there," he says. The center has already delivered some of these devices but Malloy would like to see the technology spin-off to a willing company. Another promising effort is the quantum dot infrared laser Malloy developed with Luke Lester, an assistant professor of electrical and computer engineering. They started with a project to develop quantum dot detectors. "They made lousy detectors," he says. "As we understood why, we understood they would be very good for a laser." The strengths of the semiconductor laser - it's small size and high output - are also a weakness because, unlike the conventional gas laser, atoms moving within a solid start to affect each other. As a result the light isn't as pure, but the semiconductor laser compensates in part by the ease with which it can be rapidly turned on and off. Malloy and Lester created artificial atoms (quantum dots) that can mimic the properties of real atoms in a solid. The result is a semiconductor laser with the spectral purity of a gas laser. The quantum dot laser is the first laser to demonstrate high power and high efficiency at a wavelength that can be used in communications. "It was designed, grown, packaged and tested at CHTM," he says. "We're very excited about that application." Because a laser's wavelength depends on the physical properties of the light-emitting semiconductor, scientists and engineers nationwide have devoted considerable effort to developing different materials for different applications. The FAST Center's researchers and students use CHTM's molecular beam epitaxy reactors and metal organic chemistry vapor deposition reactors to grow material, one layer of atoms at a time. In a related effort, Kaspi and fellow research engineer Andreas Stintz are developing a digital alloying technique to grow a wider range of semiconductor materials. "What our research is doing is trying to engineer Mother Nature," Malloy says. "We play tricks on very small sizes to create materials that will work in new regions and new applications. There's not always a perfect match between Mother Nature and the application, so we go about trying to change that." Malloy, who's been at UNM for 9 years, began his work in compound semiconductors (materials with two or more elements). He worked initially in microelectronic applications until he realized there were more opportunities in optoelectronics, which relies on the interplay of electrical and optical properties. "Microelectronic applications follow silicon," he says. "Optoelectronics was blazing its own path. There was a much greater opportunity to discover new things." Because most compound semiconductor materials are optically active in infrared and optical fibers work best in infrared, his research interest followed. Not all the work involves semiconductors, sensors or lasers. Some researchers are trying to understand and control the properties of dots laid down in a pattern that reflect a specific size wavelength. With CHTM director Steve Brueck's interferometric approach to patterning, they can etch a complicated pattern on a surface. Making a plane or tank invisible to infrared detection remains a long-term goal, meanwhile the center can master the ability to do such patterning and model what it might look like. The most noteworthy product of the program is students, who are now working for MicroOptical Devices and its parent company, EMCORE Corp., as well as Sandia National Laboratories, Intel and Air Force Phillips Laboratory. "Students are the best technology transfer," Malloy says. "I think we've been very successful at putting students in key places in industry and in local research labs."