Short-pulse-induced solute migration in the C₄₉H₄₃ClO₆ + 1,2 dichloroethane solution

Using the Z-scan technique with 532 nm 19 ps laser pulses separated by two time intervals τ_p-p's (0.1 s and 1.0 s) sandwiching the mass diffusion time constant of the C₄₉H₄₃ClO₆ + 1,2 dichloroethane solution, we investigate short-pulse-induced solute migration in the sample by measuring its transmittance change with τ_p-p variation. Preparing the sample at two concentrations, we find that τ_p-p reduction, from 1.0 s to 0.1 s, increases its transmittance when input pulse energy ε₁ exceeds a threshold ε_T, which is lower for the dilute solution than the concentrated one. At two ε₁'s above ε_T for the dilute solution, τ_p-p-reduction-induced transmittance increase in the dilute solution, as compared to that in the concentrated solution, is more at the lower ε₁ and less at the higher ε₁. 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.