Structure-less generation of sub-millimeter radiation

We report detailed simulations of a two-stream instability using co-propagating electron beams of differing energies By adjusting parameters such as beam currents and the energy difference, a remarkable amount of self-modulation occurs at controllable and predictable frequencies. The typical frequencies of oscillation traverse the sub-millimeter and terahertz range, and the power associated with the bunching reaches saturation in distances of propagation less than 0.1 meter.