MEASUREMENT OF EXCITED-STATE LIFETIMES IN DYE MOLECULES BY THE CURVES OF SOLUTION BLEACHING BY THE POLARIZED-LIGHT

An effect of the radiation polarization, the anisotropy of molecular absorption and emission oscillators and the time of rotational diffusion of molecules on the result has been found analytically in the method of measurement of excited state lifetimes in dye molecules by solution bleaching curves. These factors can change the ratio of the molecule lifetime to the observed solution bleaching intensity almost twofold. A neodymium laser radiation pulse 300 ps in duration has been employed to obtain bleaching curves for a number of dye solutions and to determine lifetimes of these dyes in the range from 2.5 to 130 ps. On the basis of the measurement results the dye solution No. 15 has been tested as a saturable absorber in a neodymium-doped lanthanum beryllate laser and it has been demonstrated that it offers promise for neodymium laser mode locking.