Journal of Physics D: Applied Physics   2016 年 49 卷 18 期

2016.04.07

The surface plasmon resonances of metallic nanoparticles are highly dependent on size and shape, which leads to high tunability of both linear and nonlinear optical responses. Here, we investigate the plasmon resonance and saturable absorption of gold nanorods (AuNRs) with different lengths and reveal the size dependence of electron relaxation dynamics. The strong plasmon absorption leads to ground-state bleaching and saturable absorption (SA) in AuNRs, Z-scan measurements demonstrate that the saturation threshold decreases as the length of AuNRs increases. The time-resolved differential transmittance reveals that the longer AuNRs have large relaxation times for hot electrons, which accounts for the decrease of the SA threshold.