Nonlinear optical properties of Au–Ag core–shell nanorods for all-optical switching

Au–Ag core–shell nanorods with surface plasmon resonance wavelengths of 760–840 nm were prepared. Wavelength-dependent nonlinear absorption coefficients (β) and nonlinear refractive indices (γ) of the nanorods were measured by using Z-scan techniques. The corresponding one-photon and two-photon figures of merit (W and T) were calculated from β and γ. The results show that the requirements of W > 1 and T < 1 for the application of all-optical switching could be achieved for all the samples over a broad wavelength range. These observations make the Au–Ag core–shell nanorods a good candidate for all-optical switching devices.