Picosecond degenerate four-wave mixing in colloidal solutions of gold nanoparticles at high repetition rates.

Time-resolved degenerate four-wave mixing experiments on a colloidal solution of 50-nm gold particles in acetone, using a high-repetition-rate laser source, are presented. The signal is found to depend strongly on the repetition rate of the incident radiation and above a frequency of 300 kHz is impossible to measure.