Intense and tunable multi-color terahertz radiation from laser-shaped electron beams

In this Letter, we propose what we believe to be a novel technique by combining the multi-laser pulses frequency beating and coherent undulator amplification for generating high-power multi-color terahertz (THz) radiation with tunable frequency. Numerical simulations indicate that the proposed technique can produce multi-color THz radiation with three to six distinguished colors and a peak power up to hundreds of MW, and the temporally separated two-color pulses can also be produced by employing undulators with different resonance. Due to the intrinsic properties of the proposed technique, the THz frequencies, the color number, and the frequency interval can be effectively controlled by simply adjusting the beating laser. This method paves the way for advanced application of THz pump-THz probe experiments for selective excitation of atomic multi-level systems and molecular fingerprint recognition.