ALBUQUERQUE, N.M. — From decontamination to white light generation, semiconductor based ultraviolet (UV) light sources will have many applications, including an important role in America’s security,” says Jerry Simmons, manager of Semiconductor Material and Device Science Department at Sandia National Laboratories.
One of particular interest to the Defense Advanced Research Projects Agency (DARPA) and to the Sandia research team is using UV light-emitting diodes (LEDs) in the detection of biological agents, such as anthrax. A proven technique for discriminating between weaponized bioagents and naturally occurring organisms is laser-induced fluorescence. In this technique, a UV source is focused on a sample. The pump energy excites electronic transitions and it is the flourescence from these excited molecules that indicates the presence or absence of a biological organism. The goal is to make these detectors small enough to be hand-carried by a solder or placed like a smoke detector in buildings.
Other potential uses of the UV LEDs include:
- Non-line-of-sight (NLOS) covert tactical communications. The ability to perform covert communications where line-of-sight is generally not available with very low power consumption is severely limited with conventional technologies. (Radio frequency communications technology, while highly developed, is broadly available and hence easily intercepted.) UV based transceivers will enable networked unattended sensors, small unit communications, and communications in military operations in urban terrain environments. The NLOS systems use aerosol and molecular scattering of a short wavelength optical transmitter to provide short-range communications with low probability of interception or detection.
- Light production. Through appropriate materials growth and processing, semiconductor structures can be engineered to emit at desired wavelengths. Semiconductors offer the advantages of extreme compactness, low cost, high-volume production, and lower power consumption. While they are unlikely to be used for lighting, these deep UV LEDs are enabled by basic advances in wide bandgap semiconductor materials science. Those advances can also be applied to create near-UV and visible LEDs with higher luminous efficiencies for solid state lighting.
- Water and air purification and surface decontamination. Deep ultraviolet radiation is effective at killing live bacteria and many viruses. LEDs are promising as small compact, robust, energy efficient sources of deep UV for use in water purification, either for military use or in Third World countries. UV LEDs have already been used in experimental air purifiers to break down airborne organic compounds. UV irradiation can also be used to rapidly decontaminate surfaces without the use of damaging wet chemicals, useful not only for chem-bio decontamination but also for a host of civilian and industrial applications.
- Polymer curing and chemical processing. UV illumination is used to cross-link polymers and stimulate various chemical reactions, such as epoxy curing, in industry. Examples include dental coatings to prevent tooth decay, protective polymer coatings over automobile bodies to prevent corrosion, and over optical fibers to relieve stress. Typically, these coatings are applied in liquid form, and subjected to UV to cure. But the mercury vapor lamps currently used emit large amounts of heat, fluctuate in intensity, and are expensive, fragile, and bulky.
See New Sandia UV LEDs emit short-wavelength, high-power output.
Sandia technical contacts:
- Jerry Simmons, jsimmon@sandia.gov, (505) 844-8402
- Bob Biefeld, rmbefe@sandia.gov, (505) 844-1556
- Andy Allerman, aaaller@sandia.gov, (505) 845-3697
- Art Fischer, afisch@sandia.gov, (505) 844-6543