Arbitrary Waveform Attosecond Pulse Generation
In recent years a few phenomena depending on carrier-envelope-phase (CEP) of few-cycle laser pulses were recognized. Waveform-controlled few-cycle laser pulses enabled the generation of isolated attosecond pulses and their application to the study of electron dynamics in atoms, molecules, and solids. There have been numerous proposals to produce ultrashort x-ray pulses in free-electron lasers (FELs), such as the SASE FEL. However, the temporal coherence of the output radiation is limited. In order to solve this problem, we proposed a robust method for producing waveform-controlled CEP-stable attosecond FEL pulses in the EUV spectral range. The method is based on coherent undulator radiation emitted by relativistic ultrathin electron layers, which are produced by nanobunching of a subpicosecond electron bunch, obtained from microwave electron accelerators (LINACs), in a double-period modulator undulator (MU) driven by a few-TW visible laser.