GENERATION OF FREQUENCY-CHIRPED OPTICAL PULSES IN A LARGE-SLIPPAGE FREE-ELECTRON LASER

We have investigated the optical output of the free-electron laser for infrared experiments (FELIX) when it is driven by an electron beam wi th a camped energy, We show that the applied slow ramp on the electron beam energy leads to a frequency chirp on each picosecond optical pul se, Typical values for the chirp are 0.2% frequency sweep across a 1.5 -ps-long optical pulse, The optical pulses were analyzed with a double -grating pair and with a second-order autocorrelator, The pulse durati on was reduced in the double-grating pair by 20%. A linear dependence of the chirp on the cavity desynchronization was measured.