Tight focusing of laser light using a surface plasmon polariton in a silver nano-strip and nano-ring on silica glass

In this work a solitary surface plasmon-polariton was obtained by using a frequency-dependent finite difference time-domain method for the TM- and radially polarized light at 532 nm, which was propagated through silver nano-elements (a nano-strip and a nano-ring), placed in an aqueous medium. The device's height and width were equal to 20 nm and 215 nm respectively. The intensity of surface plasmon-polariton was four times higher than that of the incident radiation. The full width at half maximum of the nanojet was 138 nm and 158 nm for the case of using a nano-strip and a nano-ring respectively.The results can be used to design devices that allow capturing and moving particles in water or other biofluids.