Calculations and measurements confirm the production of coherent broadband THz radiation from relativistic electrons with an average power of nearly 20 watts. The radiation has qualities closely analogous to the THz radiation produced by ultrafast laser techniques (spatially coherent, short duration pulses with transform-limited spectral content). But in contrast to conventional THz radiation, the intensity is many orders of magnitude greater due to a relativistic enhancement. The absorption and dispersive properties of materials in this spectral range provide contrast for a unique type of imaging [1,2]. The striking improvement in power reported here could revolutionize this application by allowing full-field, real-time image capture. High peak and average power THz sources are also critical in driving new non-linear phenomena with excellent signal to noise, and for pump-probe studies of dynamical properties of novel materials, both of which are central to future high-speed electronic devices [3,4]. It should also be useful for studies of molecular vibrations and rotations, low frequency protein motions, phonons, superconductor bandgaps, electronic scattering and collective electronic excitations (e.g., charge density waves).

Author(s): G.L. Carr, Michael C. Martin, Wayne R. McKinney, Kevin Jordan, George R. Neil, Gwyn P. Williams

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