Infrared subpicosecond laser pulses with a free-electron laser

Abstract

Subpicosecond laser pulses (down to 200 fs) have been produced and measured with a free-electron laser oscillator at a wavelength around 8.5 \ensuremath{\mu}m. This has been achieved by running our linear accelerator in a configuration where the electron bunches acquire a quasilinear time-energy relationship while traveling on the side, rather than on the crest, of an accelerating high-frequency wave.