Optical third-order nonlinearity by nanosecond and picosecond pulses in Cu nanoparticles in ion-implanted silica

We report a study of the Kerr effect and nonlinear optical absorption in a high-purity silica sample containing Cu nanoparticles prepared by ion implantation. With a vectorial self-diffraction experiment, we measured the tensorial components of the third-order nonlinear optical susceptibility response at 532 nm with pulses of 7 ns and 26 ps. We identified thermal effect as the main mechanism responsible for the nonlinear refraction in the nanosecond regime and electronic polarization for the picosecond regime. We observed saturable optical absorption in both regimes studied. We also measured the ablation threshold for this material, finding that the contribution of the linear optical absorption to the ablation threshold in each case can be different due to the presence of hot electrons.