The present invention relates to a method and an arrangement to generate a coherent electromagnetic radiation containing at most a few optical cycles in the extreme ultraviolet/vacuum ultraviolet domain. The inventive method comprises the steps of providing an electron package (15) of relativistic velocity; modulating said electron package (15) with high intensity laser light (17) in an undulator (20) having an undulator period smaller than the undulator period (u) satisfying the resonance condition, producing thereby an electron package formed of electron microbunches; and passing the electron package (15) of electron microbunches leaving said undulator (20) through a static magnetic field, and generating thereby a coherent electromagnetic radiation, wherein said static magnetic field is generated in conformity with the coherent electromagnetic radiation to be achieved. The arrangement comprises means for providing an electron package (15) of relativistic velocity; means for providing high-intensity laser light (17); a first undulator (20) arranged in the propagation direction of the electron package (15) of relativistic velocity, said first undulator being adapted to receive the electron package (16) and the laser light (17) simultaneously and to induce an interaction thereof, said interaction resulting in the microbunching of the electron package (15), wherein the undulator period of said first undulator (20) being smaller than the undulator period (u) satisfying the resonance condition; and a second undulator (3) arranged in the propagation direction of the electron package (15) after said first undulator (20), said second undulator (30) generating a magnetic field in conformity with the coherent electromagnetic radiation to be generated.

The present invention relates to a method and an arrangement to generate a coherent electromagnetic radiation containing at most a few optical cycles in the extreme ultraviolet/vacuum ultraviolet domain. The inventive method comprises the steps of providing an electron package (15) of relativistic velocity; modulating said electron package (15) with high intensity laser light (17) in an undulator (20) having an undulator period smaller than the undulator period (u) satisfying the resonance condition, producing thereby an electron package formed of electron microbunches; and passing the electron package (15) of electron microbunches leaving said undulator (20) through a static magnetic field, and generating thereby a coherent electromagnetic radiation, wherein said static magnetic field is generated in conformity with the coherent electromagnetic radiation to be achieved. The arrangement comprises means for providing an electron package (15) of relativistic velocity; means for providing high-intensity laser light (17); a first undulator (20) arranged in the propagation direction of the electron package (15) of relativistic velocity, said first undulator being adapted to receive the electron package (16) and the laser light (17) simultaneously and to induce an interaction thereof, said interaction resulting in the microbunching of the electron package (15), wherein the undulator period of said first undulator (20) being smaller than the undulator period (u) satisfying the resonance condition; and a second undulator (3) arranged in the propagation direction of the electron package (15) after said first undulator (20), said second undulator (30) generating a magnetic field in conformity with the coherent electromagnetic radiation to be generated.