Wavelength-Dependent Optical Nonlinear Absorption of Au-Ag Nanoparticles

The nonlinear optical absorption properties of Au-Ag nanoparticles (NPs) were studied using an open-aperture Z-scan under a nanosecond pulsed laser with wavelengths of 450 nm, 510 nm, 550 nm, and 600 nm. The experimental results demonstrated that, when the laser intensity was 1.04 x 10(13) W/m(2), the Au-Ag NPs showed saturated absorption (SA). When the laser intensity was increased to 3.03 x 10(13) W/m(2), the switch from SA to reverse saturation absorption (RSA) occurred. The nonlinear absorption and its transformation were analyzed by using local surface plasmon resonance (LSPR) effect, bleaching of ground state plasmon, and free carrier absorption theory.

Automated summary

Experimental results show that Au-Ag nanoparticles exhibit saturated absorption and reverse saturation absorption under different laser intensities. The transition between these two absorption states is explained by the local surface plasmon resonance effect, bleaching of ground state plasmon, and free carrier absorption theory.