Rapid-Scan Autocorrelator for Monitoring cw Mode-Locked Dye Laser Pulses

A second-order autocorrelator operating at a high repetition rate of 25 Hz was developed for the measurement of the picosecond pulse width of a cw mode-locked dye laser. The simple system consists of a Michelson-like interferometer and an assembly of retardation plates of different thickness which are mounted on an optical chopper. The pulse width is instantaneously displayed on an oscilloscope. Using this instrument, pulses as short as 1.3 ps can easily and reproducibly be obtained from a synchronously-pumped rhodamine-6G dye laser, even though the pulse-width varies critically with cavity length and other laser parameters.