Direct determination of the relaxation times of passive picosecond switches

The method of excitation and probing with picosecond light pulses was used to determine the relaxation times of various solvents of dyes № 3955, 3274, 3281, and 3323 used in mode locking of neodymium lasers. The source of exciting and probe pulses was a picosecond neodymium-doped phosphate glass laser operating at a repetition frequency of 2 Hz. The results were analyzed and the experiment was controlled by a microcomputer. A comparison of the results obtained with those deduced from indirect measurements indicated that the latter underestimated seriously (by a factor of 2–10) the relaxation times.