Optical Autocorrelation Function of a 3.2-μm Free-Electron Laser

The width of the picosecond optical pulses produced in the Stanford University 3-\ensuremath{\mu}m free-electron laser has been measured by using optical autocorrelation techniques. The pulse width was measured as a function of cavity length detuning and compared with the laser linewidth. The optical pulses are nearly transform limited and somewhat shorter than expected at large values of the cavity length detuning.