Particle beam modulation techniques for the generation of subfemtosecond photon pulses in the VUV/soft X-ray range

In this paper we consider the energy modulation of a short subinterval of an electron bunch at the scale length of visible/UV laser light. Possibilities for converting this modulation into a high-gain FEL-type density fluctuation to produce a coherently-enhanced subfemtosecond radiation pulse in the VUV/soft X-ray range are discussed.