Spectral dependence of third-order susceptibility of Au triangular nanoplates

We experimentally investigated the spectral dependence of the third-order susceptibility [Formula: see text] of Au triangular nanoplates in a broad wavelength region (400-1,000 nm). Complex shaped plasmonic nanoparticles provide a promising route to achieve control of their optical properties at the nanoscale. However, little is known about the effects of geometrical parameters to the optical nonlinearities and underlying mechanisms of the plasmon modes. Here, we obtained the [Formula: see text] of Au triangular nanoplates featuring a narrow plasmon resonance that is tunable in the visible and near-IR regions. This work demonstrates that the plasmonic triangular nanoplates simultaneously shows self-focusing and -defocusing, and saturable and reverse-saturable absorption properties at specific wavelength regions. Maximum amplitudes of real and imaginary components are - 6.8 × 10^-18 m²/V² at 668 nm and - 6.7 × 10^-18 m²/V² at 646 nm, respectively. Spectral dependence of the quantity [Formula: see text] enables comparison between different shaped plasmonic NPs to boost active plasmonic applications performance.