Optical nanoantenna based on an asymmetric nanohole pair milled in an opaque gold film

The optical interaction of two asymmetric nanoholes milled in an opaque gold film through surface plasmon polariton (SPP) propagation is investigated. It is shown that the interaction between the nanoholes strongly depends on the polarization direction of the incident light. Moreover, it is found that the asymmetric nanohole pair can direct the incident light. The directivity of the nanohole pair depends on the separation distance between the nanoholes, which leads to in-phase and antiphase interaction of the nanoholes. For short distances (comparable to the SPP wavelength launched by each nanohole) the interaction can be considerable, in contrast to the high separation distance, which leads to weaker interaction between the nanoholes. The interaction mechanism of the nanoholes has been supported by the magnetic-coupled dipole approximation method. (C) 2015 Optical Society of America