Near-field switching and focusing using plasmonic nanostructures with different polarizations

Abstract

In this paper, the near field distribution patterns excited from half spiral nanoslits and gratings are investigated. The various near field distribution patterns observed are due to the interference of propagating surface plasmon emerging from the nanoslits or gratings. The half spiral nanoslits are incident with left and right-handed circular polarization. The resulting focal spots are found at different positions for left (LHC) and right-handed circular (RHC) polarizations. This is due to the change in phase difference of propagating surface plasmon waves emerging from the nanoslit when excited by different circular polarizations. The distance between the focal spots for left and right-handed polarizations is λ spp /2. In addition, the half spiral nanoslit is also illuminated with linear polarization in different rotational angles. This paper also includes the near field distributions that result from the interference of surface plasmon polariton fields with partial spiral shape. It is believed that these interesting field patterns due to different arrangements of nanoslits could be used for trapping molecules, near field imaging and sensing.