Short-pulse-induced solute migration in the CHClO + 1,2 dichloroethane solution.

Using the Z-scan technique with 532 nm 19 ps laser pulses separated by two time intervals τ's (0.1 s and 1.0 s) sandwiching the mass diffusion time constant of the CHClO + 1,2 dichloroethane solution, we investigate short-pulse-induced solute migration in the sample by measuring its transmittance change with τ variation. Preparing the sample at two concentrations, we find that τ reduction, from 1.0 s to 0.1 s, increases its transmittance when input pulse energy ε exceeds a threshold ε, which is lower for the dilute solution than the concentrated one. At two ε's above ε for the dilute solution, τ-reduction-induced transmittance increase in the dilute solution, as compared to that in the concentrated solution, is more at the lower ε and less at the higher ε. This differs from continuous-wave-driven thermal diffusion which always causes a larger transmittance increase in the concentrated solution by inducing a larger temperature gradient. From this study, we predict that solute migration induced by short pulses at 1064 nm is one of the undesired heating effects occurring when this solution is used to simultaneously Q-switch and mode-lock Nd:YAG lasers.