Terahertz Free-Electron Lasers with Bragg Structures Based on the Coupling between Traveling and Quasicritical Waves

The possibility of creating high-power tunable planar terahertz free-electron lasers based on modified Bragg structures with the coupling of paraxial and transverse (with respect to the velocity of particles) wave fluxes has been demonstrated. In addition to the compatibility with the transport channels of intense electron beams, the advantage of the proposed structures is the spatial coherence of radiation at a large oversize factor of the interaction region in two transverse coordinates.