This Small Business Technology Transfer (STTR) Phase I research project will determine the feasibility of developing new solid-state devices based on photomixing (optical heterodyning) in laser-assisted field emission to generate terahertz (THz) radiation. Many THz applications are now under study, including air quality monitoring, cancer detection, and security screening of packages and personnel. However, researchers describe ""hurdles"" due to the present THz sources, including limited tunable bandwidth and output power. Photomixing is now used in sources of THz radiation, and the PI has made a new type of microwave tube that, in effect, creates a nanoscale ultrafast non-linear optical medium for photomixing in laser-assisted field emission. Analyses show that this new technique may lead to THz sources having much greater tunable bandwidth and output power because of the high-speed and nonlinearity of field emission and the considerable reduction in the shunting capacitance. It is proposed to use silicon nanotechnology to develop solid-state devices that operate at atmospheric pressure because they should be much easier to manufacture and market than the vacuum tubes which the PI made earlier. The Phase I objective is to build and test prototypes having an output power of 80 nW at 1 THz to show feasibility. If this project is successful in developing new solid-state sources for terahertz (THz) radiation, the increased power and bandwidth could help in many THz applications including science (astronomy, biology, and chemistry), medicine (cancer detection and dental imaging), and security technology (detecting non-metallic concealed weapons and explosives). This project could also lead to progress in high-speed computing and communications where massive paralleling of much slower devices is now required. Thus, there could be a far-reaching impact to benefit science, industry, and society, to open a strong market. This project may also contribute to basic science. A resonance of optical radiation with tunneling electrons, discovered in simulations and later confirmed by experiments, is fundamental to this technology. This resonance requires that a significant correction be made in determining the local density of states in metals by photofield spectroscopy, and it provides some insight in regard to the process of barrier penetration including the long-debated topic of the duration of quantum tunneling
