High-Order Nonlinearity of Surface Plasmon Resonance in Au Nanoparticles: Paradoxical Combination of Saturable and Reverse-Saturable Absorption

The remarkable nonlinear effects of surface plasmon resonance in Au nanoparticles, mainly the third-order and fifth-order nonlinearities, are responsible for saturable absorption and reverse-saturable absorption, respectively, with a switch in the nonlinear absorption behavior at 5 GW cm−2. By employing the saturable absorption effect of Au nanoparticles, a passively Q-switched solid-state pulsed laser is successfully demonstrated at the wavelength of 1.06 μm.