Harmonics in a Quantum Free Electron Laser: Towards a compact, coherent γ-ray source

► Quantum Free Electron Lasers (QFELs) could emit monochromatic, coherent short-wavelength radiation due to the discrete nature of the electron-radiation momentum exchange during photon emission. ► A SASE-QFEL may offer the possibility to produce intense, coherent γ-rays via harmonic generation. ► The use of harmonics allows the generation of coherent radiation at shorter wavelengths for a given electron beam energy and beam quality.