Warfighters need to be able to detect and identify biological and chemical agents that may be in use by enemy forces. Current detection methods require large, heavy equipment, and a great deal of power. To address these deficiencies, the Compact Mid-Ultraviolet Technology (CMUVT) program is developing the essential heteroepitaxy, waveguides, cavities, contacts, and micro/nanostructures necessary to enable efficient LEDs and chip-scale semiconductor lasers operating at wavelengths below 275 nm.
The middle ultraviolet (UV) spectral region (200-300 nm) is of significant interest to DoD for applications involving detection, identification and decontamination of biological and chemical agents. Amino acids and many other common biological molecules are absorbing at these wavelengths, and the resulting near UV (300-400 nm) and visible fluorescence can signal their presence and aid in their identification in aerosol clouds, liquid suspensions or powders. Spectroscopic identification via Raman scattering is enhanced for excitation in the mid-UV because the Raman cross section is increased several orders of magnitude, and there is little to no fluorescence background at these wavelengths to obscure the scattered signal. Many absorption bands also exist at these wavelengths to increase the efficacy of intense UV irradiation for sterilization and chemical decontamination.
Mature laser and detector technologies exist in the mid-UV. Large excimer lasers, such as KrF (248 nm), are common tools for lithography. A small Q-switched laser with 4th harmonic generation and a photomultiplier tube are currently used in company- and battalion-level chem/bio detection systems, such as the Joint Biological Point Detection System. However, all these systems are too heavy, fragile and expensive for widespread expeditionary deployment at levels from platoons down to the individual warfighter. Realizing semiconductor solutions for bright, efficient light-emitting diodes (LEDs) and lasers across the mid-UV wavelength regime will provide the critical path to compact future systems.
CMUVT will pursue two primary tracks targeting LEDs at 250-275 nm with an output of 100 mW with 20 percent wall-plug efficiency and lasers producing 10 mW between 220 and 250 nm without nonlinear frequency conversion. A secondary effort will investigate bulk AlN substrates. The majority of the program will address the fundamental material and device challenges that currently limit the performance of group III-nitride-based semiconductor devices in the mid-UV. The resulting UV components will significantly improve the size, weight, power, and capability of chemical/biological-agent detectors, portable water purification illuminators and other UV-dependent applications of commercial interest.
Dr. Daniel Greendaniel.email@example.com