Saturable absorption (SA) and reverse saturable absorption (RSA) at 532 nm were observed in Ag nanodots prepared by pulsed laser deposition. The real [Re χ(3)] and imaginary [Im χ(3)]] parts of the third order nonlinearity of these films were measured using the Z -scan technique. At low input irradiances, the decrease in absorption near the focal point results from a negative Im χ(3)] and yields SA. At higher input irradiance, RSA becomes dominant. The transition from SA to RSA suggests that there is a threshold irradiance at which additional nonlinear process(es) is (are) involved and become dominant. The recovery time of these nonlinear processes was measured by a degenerate pump-probe experiment. The effects are explained in terms of the electron dynamics in the excited states.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)