TRANSFORM-LIMITED COHERENT SYNCHROTRON-RADIATION WAVEPACKETS IN A CHIRPED PULSE FREE-ELECTRON LASER

A novel source of transform-limited pulses of coherent electromagnetic radiation relying on the synchrotron radiation process in a fast wave guiding structure is investigated theoretically. An ultrashort electr on bunch transversally accelerated by a periodic external field is con sidered. At grazing, where the bunch and group velocities are matched, the duration of the resulting ultrawideband chirped pulse is governed by group velocity dispersion instead of slippage. Because of the inti mate connection between the rate of chirping and the bandwidth, the co rresponding pulse duration is shown to be very close to the Fourier tr ansform limit. In addition, the propagation of such chirped pulses thr ough a guiding structure with negative group velocity dispersion is in vestigated both theoretically and computationally. The spectral and te mporal characteristics of the chirped and compressed pulses are derive d analytically. Detailed computer calculations complement this theoret ical analysis. (C) 1996 American Institute of Physics.