Boston University's professor Theodore Moustakas of the electrical and computer engineering department has received a $1.5 million, two-year subcontract from DARPA to help develop a handheld, electron-beam pumped semiconductor laser that would be the first to operate within the ultraviolet region. Because of its ultralow emission wavelength and compact size, such a laser could be exploited for a wide range of defense and commercial applications, including non-line-of-sight communication in dense urban areas and other military theaters, via airborne particulates that propagate the signal; identification of biological and chemical substances used in potential terror attacks; and point-of-care chemical analyses of blood and other bodily fluids. Professor Theodore Moustakas (ECE) inspecting the growth of nitride-based semiconductor materials. (Image: BU) To develop this unprecedented laser technology, Moustakas and two co-investigators, Associate Professor Roberto Paiella and Assistant Professor Luca Dal Negro will fabricate UV laser materials and component devices. Applied Physics Technologies and the Jet Propulsion Laboratory will design miniature electron guns to pump the laser, and Photon Systems Inc., the prime contractor, will integrate everything into a prototype sized below one cubic inch. “We plan to make a laser structure that, when bombarded with an electron beam, produces pairs of electrons and holes (positively charged particles), which recombine and produce the UV light,” said Moustakas. “DARPA chose us because we have produced aluminum gallium nitride alloys in which up to 68 percent of those electron/hole pairs are converted into light, a conversion efficiency of about 1000 times that of materials produced by other research groups.” Using an atom-by-atom assembly technique called molecular beam epitaxy, the ECE research team will produce the core laser material, aluminum gallium nitride, and then construct component devices from multiple layers of the material. The researchers will evaluate the materials by directing electron beams at them in the lab. In parallel with this project, Moustakas is working on a separate grant from NASA to develop a similar laser to perform chemical analyses of soil samples on future Mars expeditions. He is also advancing visible and ultraviolet LEDs and lasers for solid-state white lighting, water and air sterilization, and identification of biological and chemical agents; and indium gallium nitride “quantum dots” that boost solar cell efficiency. For more information, visit: www.bu.edu