Proposal for sub-femtosecond pulse generation with controlled carrier-envelope phase

A robust method for producing few-cycle pulses with controlled waveform in the EUV-VUV spectral range by coherent undulator radiation of relativistic ultrathin electron layers produced by inverse free-electron laser (IFEL) action is proposed. The realization of such exceptional pulses will enable time- and CEP-resolved measurements with less than 100 as resolution.