Enhanced inverse Faraday effect and time-dependent thermo-transmission in gold nanodisks.

Nonmagnetic media can be magnetized by light via processes referred to as an inverse Faraday effect (IFE). With nonmagnetic metal nanostructures, the IFE is dominated by the presence of light-induced solenoidal surface currents or plasmons with orbital angular momenta, whose properties depend on both the light and nanostructure geometry. Here, through a systematic study of gold nanodisks with different sizes, we demonstrate order-of-magnitude enhancement of the IFE compared to a bare gold film. Large IFE signals occur when light excites the dipolar plasmonic resonance of the gold nanodisk. We observe that the spectral response of the IFE signal mirrors the spectral response of time-dependent thermo-transmission signals. Our careful quantitative experimental measurements and analysis offer insight into the magnitude of IFE in plasmonic structures for compact, low-power, magneto-optic applications.